sh-Polypeptide-71 for Hair Regrowth

Evidence Review created on 08/25/2026 using AI4L / Opus 5

Also known as: Recombinant Human Vasoactive Intestinal Peptide, rh-VIP, sh-Polypeptide-65, VIP Peptide, Clairesome-VP

Motivation

sh-Polypeptide-71 is a laboratory-made copy of a small human signalling molecule that nerve endings release into the skin. It appears on cosmetic labels under this code name and is sold almost entirely inside multi-ingredient scalp serums marketed for thinning hair. Its appeal rests on one idea: a messenger that widens small blood vessels and calms irritation in skin might also improve conditions around the hair root.

The molecule it copies was first isolated from the gut in 1970 and later found throughout the nervous system and the skin, including the nerve fibres that wrap around hair roots. Laboratory work has since tied it to blood-vessel growth, to the movement and multiplication of skin cells, and to the immune quiet that healthy hair roots normally maintain. Scalp serums built on that reasoning reached clinics around 2020.

This review examines what is known about sh-Polypeptide-71 for hair regrowth: how it is proposed to act, what human and laboratory evidence exists and how strong it is, what risks and unknowns come with it, and how it is used in practice.

Benefits - Risks - Protocol - Conclusion

Grokipedia

No Grokipedia article exists for sh-Polypeptide-71.

Examine

No Examine article exists for sh-Polypeptide-71. Examine covers orally ingested dietary supplements and nutrients; a topically applied recombinant cosmetic peptide falls outside the scope of its database.

ConsumerLab

No ConsumerLab article exists for sh-Polypeptide-71. ConsumerLab tests ingested supplements for identity and purity and does not review topical cosmetic peptides.

Systematic Reviews

No systematic reviews or meta-analyses for sh-Polypeptide-71 were found on PubMed as of August 25, 2026.

The trade-off at the centre of this intervention is unrepresented on both sides: neither the claimed effect (hair regrowth) nor the principal risks (scalp irritation and loss of hair shaft pigmentation) has been examined in a systematic review or meta-analysis of this ingredient, because no primary trial of it exists to review.

Mechanism of Action

sh-Polypeptide-71 is the INCI designation (International Nomenclature of Cosmetic Ingredients, the standard naming system printed on cosmetic labels) for a recombinant, meaning laboratory-produced, copy of human vasoactive intestinal peptide. The native molecule is 28 amino acids long and acts through the VPAC1 and VPAC2 receptors, which switch on the cyclic AMP cascade (an internal signal-amplifying relay). Human scalp follicles express both receptors in their epithelium, and nerve fibres running alongside the follicle release VIP locally, as shown by Bertolini et al..

Three strands are proposed. Blood supply: VIP dilates skin vessels and raises production of VEGF (vascular endothelial growth factor, the principal driver of new blood-vessel formation) in human keratinocytes (the main cell type of skin and follicle), reported by Kakurai et al.. Epithelial activity: VIP stimulates keratinocyte multiplication through cyclic AMP (Haegerstrand et al.). Immune quiet: VIP protects the follicle’s shielded-from-immune-attack state.

A competing reading of the same signalling is unfavourable. VIP is augmented in psoriatic skin (Pincelli et al.) and induces keratinocyte release of interleukin-6 and interleukin-8 (Kakurai et al.), and it suppresses follicular pigment production (Gomez et al.).

Pharmacologically, VIP has a plasma half-life near one minute, is cleared by peptidases including DPP-4 (dipeptidyl peptidase-4, an enzyme that clips peptide chains), is not handled by liver CYP enzymes (cytochrome P450 drug-metabolising enzymes), and after topical use its distribution is capped by the stratum corneum (the skin’s outer barrier layer).

Historical Context & Evolution

Vasoactive intestinal peptide was isolated from porcine intestine in 1970 as a vasodilator hormone, and was studied for decades as a gut and nervous-system messenger rather than as a therapy. Its first therapeutic incarnation was aviptadil, a synthetic full-length VIP developed for pulmonary hypertension, sarcoidosis, and erectile dysfunction, and later trialled intravenously in critical respiratory failure.

Those drug trials are instructive rather than settled. A 196-patient placebo-controlled trial reported no significant benefit on its primary endpoint but a doubling of the odds of 60-day survival (Youssef et al.), while the larger publicly funded TESICO trial of 461 patients found no improvement in its primary outcome and no mortality difference (Brown et al.). What changed between them was scale, blinding, and independence of funding; the smaller positive trial was sponsor-run, the larger null trial was government-funded. Neither result addresses topical scalp use, and the drug programme’s difficulties do not settle the cosmetic question either way.

The cosmetic use came separately. The ingredient entered cosmetic nomenclature as sh-Polypeptide-65, later renumbered sh-Polypeptide-71, and was first marketed for eye-area puffiness, redness, and barrier repair. Its migration into scalp products followed the observation that hair follicles are densely innervated by VIP-containing nerve fibres and that blood supply around the follicle declines in pattern hair loss. Multi-peptide scalp serums containing it reached clinical practice around 2020.

Expected Benefits

High 🟩 🟩 🟩

No benefit reaches High: the class of evidence required, a replicated human clinical or validated-surrogate outcome such as hair count or shaft diameter measured in more than one trial, does not exist for this ingredient in any formulation.

Medium 🟩 🟩

No benefit reaches Medium either: there is not even a single controlled human trial, nor consistent observational data, measuring a hair outcome for a product identified by this ingredient.

Low 🟩

Increased Hair Density and Shaft Diameter Within Multi-Peptide Scalp Serums ⚠️ Conflicted

A seven-peptide complex containing sh-Polypeptide-71 is claimed to thicken hair shafts and raise density. The supporting human data are uncontrolled and sponsor-linked. The one independent trial of a growth-factor hair serum was null (Mann et al.). Net reading: the positive signal rests entirely on the seller’s own uncontrolled reports.

Magnitude: Direction is toward greater hair density and shaft diameter, reaching statistical significance over six months, and it holds only under laser-assisted delivery in a ten-participant uncontrolled pilot (Taub et al.) published in Hair Transplant Forum International, the journal of the International Society of Hair Restoration Surgery, whose members earn revenue from the hair-restoration procedures this product supports, co-authored by the formulation’s own developer. The literature reports no outcome figure for any formulation containing sh-Polypeptide-71, and no controlled trial has measured hair count or shaft diameter for one.

Speculative 🟨

Improved Blood Supply Around the Follicle

VIP dilates skin vessels and raises keratinocyte output of VEGF, the main driver of new vessel growth (Kakurai et al.). Basis is cell culture only; no human scalp perfusion measurement exists.

Protection of Hair Follicle Immune Privilege

In cultured human scalp follicles, VIP protected the follicle’s shielded-from-immune-attack state against experimentally induced collapse (Bertolini et al.). Basis is isolated-organ culture; no controlled study has tested this in people.

Follicular Keratinocyte Proliferation

VIP stimulates multiplication of cultured human keratinocytes through cyclic AMP (Haegerstrand et al.). Basis is laboratory assay only; whether follicle keratinocytes respond the same way is untested.

Reduced Scalp Inflammation and Flaking

Supplier documentation claims that this peptide reduces redness and flaking in irritated skin. Basis is unpublished vendor material plus VIP’s immune-dampening actions in laboratory models; no controlled scalp study exists.

Benefit-Modifying Factors

Receptor gene variants: Variants of VIPR1 (the gene encoding the VPAC1 receptor) alter receptor levels and VIP signalling in human cells (Delgado et al.), so identical application may produce unequal follicular signalling between individuals; VIPR2 is untested.
Baseline biomarker status: Low ferritin (the stored-iron protein), low vitamin D, and untreated thyroid dysfunction each independently restrict hair shaft growth. Where any of these is uncorrected, a topical signalling peptide cannot supply the missing substrate and apparent response is blunted.
Sex-based differences: Female pattern loss is diffuse with a retained frontal hairline and often preserved follicle counts, leaving more headroom for a serum acting on shaft calibre. Male vertex loss with advanced miniaturisation (progressive shrinking of follicles) leaves fewer responsive follicles.
Pre-existing conditions: In alopecia areata, VPAC receptor protein is significantly reduced in affected hair bulbs (Bertolini et al.), meaning the target itself is downregulated in exactly the condition where the signal might be most wanted.
Age: Older scalps have thinner skin and reduced vessel density around follicles, which may raise peptide penetration while lowering the number of follicles still able to re-enter a growth phase. Adults past sixty see proportionally smaller visible change.

Potential Risks & Side Effects

High 🟥 🟥 🟥

No risk reaches High: the class of evidence required, a documented adverse event or validated clinical measure recorded in more than one trial of this ingredient, does not exist, because no trial of the ingredient has been run.

Medium 🟥 🟥

No risk reaches Medium either: there is no single controlled trial and no consistent observational safety dataset for any product identified by this ingredient.

Low 🟥

Application-Site Irritation and Contact Sensitisation

These are leave-on serums whose carriers include curcumin, phenoxyethanol, and copper tripeptide-1, all recognised contact sensitisers; the manufacturer warns against curcumin allergy. In the only independent trial of a growth-factor hair serum, twenty patients reported minimal discomfort and no serious application-site events (Mann et al.). Reactions reverse on stopping.

Magnitude: Direction is toward mild, transient redness and stinging, concentrated in the first two weeks and in people with pre-existing seborrhoeic dermatitis (a common flaky, inflamed scalp condition) or a disrupted scalp barrier; the literature reports no incidence figure for any sh-Polypeptide-71 formulation, and the ingredient has never been patch-tested in isolation.

Vasoactive Effects at Systemic Exposure

Intravenous VIP in healthy volunteers produced flushing, a raised pulse rate, and widened blood-pressure amplitude (Domschke et al.), the picture of Verner-Morrison syndrome (the watery-diarrhoea illness caused by VIP-secreting tumours). Evidence is indirect: the route is infusion, not scalp application. Relevance rises only where microneedling or laser breaches the barrier.

Magnitude: Flushing and pulse-rate increase appeared at an infusion of 3.3 pmol/kg/min producing plasma concentrations in the tumour-syndrome range, and plasma half-life is roughly one minute; no measurable systemic peptide exposure has been demonstrated after topical scalp use, and no figure exists for that route.

Speculative 🟨

Loss of Hair Shaft Pigmentation

In cultured human scalp follicles VIP acted as a negative regulator of pigmentation (Gomez et al.). Basis is isolated-organ culture only; no human study has tracked hair colour during use.

Amplified Cutaneous Inflammatory Signalling

VIP is augmented in psoriatic lesions (Pincelli et al.) and induces keratinocyte release of interleukin-6 and interleukin-8 (Kakurai et al.). Basis is cell-line work only; no flares from topical use are reported.

Angiogenic Stimulation of Undiagnosed Scalp Lesions

VIP raises VEGF output from keratinocytes (Yu et al.), and the manufacturer excludes anyone with prior scalp skin cancer. Basis is mechanistic reasoning only; no case reports connect this ingredient to lesion growth.

Risk-Modifying Factors

Receptor gene variants: VIPR1 variants alter VPAC1 receptor levels and VIP signalling in human cells (Delgado et al.), so the vasodilatory and inflammatory response may run stronger in some individuals; none has been tested against scalp tolerance.
Peptide-clearing enzyme activity: DPP-4 is a principal degrader of VIP, and blocking it raises local peptide levels (Jungraithmayr et al.). People taking DPP-4-inhibiting diabetes medication may sustain higher local concentrations than intended.
Baseline biomarkers: No biomarker predicts tolerance, and none is validated for this purpose. Elevated high-sensitivity C-reactive protein or an active scalp inflammatory picture flags skin more likely to sting or flare on a leave-on peptide serum.
Sex-based differences: Women apply more layered scalp products, raising cumulative exposure to inactive formulation ingredients and sensitisation odds, and report flushing more often. No sex difference in peptide response itself has been measured.
Pre-existing conditions: Psoriasis, atopic dermatitis (eczema), and mastocytosis (a disorder of excess mast cells) all involve heightened neuropeptide-driven inflammation, the same pathway this ingredient engages. Prior scalp skin cancer is an explicit manufacturer exclusion.
Age: Older skin has a thinner, more permeable barrier and slower repair, raising irritation risk, while taking several medications at once raises the chance of concurrent DPP-4 inhibitor or vasodilator use. Protocols for adults past seventy introduce it more slowly.

Key Interactions & Contraindications

Topical minoxidil (Rogaine, Kirkland): Caution. Both act partly by widening scalp vessels, so combined use plausibly increases redness, itch, and transient shedding. Applications are separated by at least thirty minutes, and one agent is introduced at a time.
Topical prescription retinoids and exfoliating acids (tretinoin, adapalene, glycolic acid, salicylic acid): Caution. Barrier disruption raises peptide penetration and irritation together. Alternate-night use rather than layering is standard; the acid is withdrawn if stinging persists beyond a week.
Over-the-counter medicated shampoos (ketoconazole 1%, selenium sulfide, coal tar, salicylic acid): Monitor. These strip lipids and residue, removing the leave-on serum and raising irritation. The serum is applied to a dry scalp on non-shampoo evenings.
Microneedling devices and fractional laser (1927 nm thulium): Monitor. Device-assisted delivery is the intended clinical use but sharply increases absorption and irritation. Clinic protocols space sessions two to four weeks apart and apply the serum immediately after the pass.
Systemic DPP-4 inhibitors (sitagliptin, linagliptin, saxagliptin): Theoretical caution. These slow enzymatic breakdown of the parent peptide (Jungraithmayr et al.), potentially raising local exposure. No clinical consequence has been reported; increased scalp flushing would be the observable sign.
Supplements with additive scalp vasodilation (topical caffeine, rosemary essential oil, Ginkgo biloba extract, niacinamide, topical melatonin): Caution. Additive redness, warmth, and stinging. One at a time is the usual approach, and niacinamide is already present in the leading formulation.
Supplements with additive follicular signalling (copper tripeptide-1, biotinoyl tripeptide-1, saw palmetto, oral collagen peptides): Monitor. No documented adverse interaction, but stacking makes it impossible to attribute either a benefit or a reaction to any single agent.
Other interventions (platelet-rich plasma injection, low-level laser caps, hair transplantation): Monitor. Clinics commonly combine these with peptide serums after the procedure; the added irritation on freshly treated or grafted scalp is the practical concern, not a pharmacological conflict.

Populations who should avoid sh-Polypeptide-71:

Anyone with a history of scalp keratinocyte carcinoma (basal cell or squamous cell skin cancer) or scalp melanoma at any time, given untested vessel-promoting and proliferative signalling
Active scalp infection, including bacterial folliculitis (infected hair follicles) and tinea capitis (scalp ringworm), until a clinician confirms it has cleared
Scarring alopecias (lichen planopilaris, frontal fibrosing alopecia, and central centrifugal cicatricial alopecia, where follicles are destroyed rather than dormant)
Moderate-to-severe scalp psoriasis or atopic dermatitis, meaning disease affecting more than 10% of body surface area or requiring systemic therapy
Pregnancy and lactation, and anyone under 18 years of age
Known allergy to curcumin, phenoxyethanol, copper peptides, or any other component of the specific formulation

Risk Mitigation Strategies

Patch test before scalp-wide use: One drop is applied to a 2 cm² area behind the ear daily for three days and inspected at 48 and 72 hours. Prevents scalp-wide contact dermatitis from curcumin or preservative sensitivity.
Dermatological scalp examination before starting: Any pigmented or crusted scalp lesion is assessed by a clinician first. Mitigates the untested risk of applying a vessel-promoting peptide over an undiagnosed skin cancer.
Once-daily start rather than twice daily: A single evening application for the first four weeks precedes any move to the twice-daily label regimen. Mitigates early irritation and stinging, the most commonly reported complaint.
Four-week delay before device-assisted delivery: Microneedling and fractional laser are withheld until daily topical tolerance is established. Mitigates the amplified absorption and irritation that accompany a deliberately breached skin barrier.
Separate nights for barrier-disrupting actives: Tretinoin, glycolic acid, and salicylic acid are used on alternate nights rather than layered. Mitigates the combined penetration-plus-irritation effect that drives most discontinuations.
Fixed-site photography at baseline, 12 and 24 weeks: A 1 cm² vertex site is photographed under identical lighting and parting. Detects hair lightening or accelerated shedding early enough to stop before a full hair cycle is spent.
One scalp agent introduced at a time: Four weeks separate the addition of minoxidil, a peptide serum, and any oral agent. Prevents mis-attributing either a reaction or a benefit to the wrong product.

Therapeutic Protocol

Standard at-home regimen: One full dropper, roughly 1 mL, of the peptide solution massaged into a dry scalp over thinning areas once daily and not rinsed. A 50 mL bottle supplies about fifty applications.
Manufacturer’s twice-daily variant: The original label instruction was morning and evening application with vigorous rub-in. Later product documentation moved to once daily, so both regimens circulate; neither has been tested against the other.
In-office device-assisted regimen: A 1927 nm fractional thulium laser or microneedling pass followed immediately by the higher-concentration in-office serum, repeated every two to four weeks for twelve weeks, then maintained at home.
Popularised by: The device-plus-serum approach was developed around the KeraFactor and KeraLase products by dermatologist Amy Forman Taub with biotechnologist James Bartholomeusz, and is promoted by hair-restoration practices including Ziering Medical.
Competing drug-first approach: Many clinicians treat pattern loss first with minoxidil and an oral 5-alpha-reductase inhibitor (finasteride or dutasteride, which block the hormone that shrinks follicles), adding peptide serums only afterwards. The two sequences have never been compared.
Best time of day: Evening application on a dry scalp is standard, since the serum is left on for hours and daytime sweat, styling products, and washing remove it. No circadian advantage has been demonstrated.
Half-life: The parent peptide clears from plasma with a half-life near one minute (Domschke et al.). Residence time in scalp tissue after topical liposome-encapsulated delivery has not been measured.
Single versus split dosing: Because tissue residence is unmeasured, split dosing rests on an assumption of rapid local degradation rather than on data. Once-daily use is the practical default; twice daily doubles cost and irritation exposure.
Genetic considerations: VIPR1 variants alter VPAC1 receptor levels and signalling (Delgado et al.). No pharmacogenetic test guides dosing, and no clinic protocol adjusts for genotype.
Sex-based differences: No dosing difference is specified. Women with diffuse thinning typically apply across a wider midline field, men over the vertex and temples; total volume per application is the same.
Age considerations: Protocols for adults past sixty-five begin at half the volume for two weeks given thinner scalp skin, with response expected only where miniaturised rather than absent follicles remain.
Baseline biomarkers: Low ferritin, low vitamin D, and thyroid dysfunction are corrected before response is judged, since these cap hair shaft growth independently of any topical signal.
Pre-existing conditions: Active seborrhoeic dermatitis is controlled first in practice, since an inflamed scalp both stings on application and confounds any assessment of shedding.

Discontinuation & Cycling

Intended duration: Use is open-ended. The manufacturer frames it as maintenance of gains achieved through in-office treatment, with best results stated at twelve to eighteen months, which implies indefinite continuation.
Withdrawal effects: None described, and none expected pharmacologically given a peptide with a one-minute plasma half-life and no receptor-dependence syndrome. No rebound shedding has been reported.
Expected regression after stopping: Any gain in shaft calibre should fade over one full hair cycle, roughly three to six months, as follicles revert to their untreated growth phase. This is extrapolated, not measured.
Tapering: Not pharmacologically necessary. Some practitioners step down to alternate-day application to reduce cost while observing whether density holds, which doubles as a personal on-off test.
Cycling: No evidence supports scheduled cycling. Receptor downregulation under continuous stimulation is plausible in principle but has not been demonstrated for VPAC receptors in skin.

Sourcing and Quality

Label declaration: Verification rests on finding “sh-Polypeptide-71” verbatim in the ingredient list. Older stock may still carry the retired designation sh-Polypeptide-65, and unrelated numbers such as sh-Polypeptide-1 or sh-Polypeptide-11 are different molecules.
Undisclosed concentration: No supplier publishes the amount per bottle, and cosmetic labelling does not require it. Position in the ingredient list is the only available proxy, and it appears last in the leading formulations.
Absent third-party testing: No pharmacopoeial monograph exists for this ingredient. The available substitutes are registration under the US Modernization of Cosmetics Regulation Act and a batch certificate of analysis supplied on request.
Stability and storage: Recombinant peptides degrade with heat and freeze-thaw. Labels specify storage below room temperature without freezing and discard at the period-after-opening mark; summer shipping without temperature control is a real risk.
Established brands: KeraFactor by SkinQRI supplies both the at-home Scalp Stimulating Solution and the in-office MD serum; the HydraFacial Keravive Peptide Spray is the other widely distributed product containing it.
Research-grade peptide vendors: Powders sold as research-only vasoactive intestinal peptide or aviptadil are not cosmetic-grade, carry no identity testing, and are formulated for injection rather than topical use. Compounding pharmacies do not supply this ingredient.

Practical Considerations

Time to effect: The manufacturer states reduced shedding and visible volume at eight to twelve weeks, fuller results at four to six months, and best results at twelve to eighteen months. No independent source confirms any of these timings.
Common pitfalls: Expecting the single peptide to act alone when it is one of seven or more actives; stopping before one full hair cycle; applying to damp hair straight after washing; and substituting it for agents with controlled evidence.
Regulatory status: It is a cosmetic ingredient in the United States and the European Union, not an approved medication. No efficacy claim for hair loss has been reviewed by the Food and Drug Administration or the European Medicines Agency.
Cost and accessibility: The at-home solution lists at about USD 174 for 50 mL, roughly fifty daily applications, or about USD 100 to 125 monthly. In-office laser-plus-serum sessions add several hundred dollars each and require a participating clinic.
Payer and clinic incentives: Pattern hair loss is rarely reimbursed, so insurers exert no pressure either way. The financial incentive sits with clinics selling both the device sessions and the take-home serum, which is also where the favourable reports originate.

Interaction with Foundational Habits

Sleep: No direct interaction. Vasoactive intestinal peptide is the principal synchronising signal of the brain’s master circadian clock, but a topically applied peptide with a one-minute plasma half-life does not reach it, and no sleep disturbance has been reported. Evening application is convenient rather than driven by body-clock timing.
Nutrition: Indirect and permissive. Adequate protein, iron, zinc, and vitamin D are prerequisites for hair shaft synthesis, and deficiency in any of them masks a topical signal. No food, fasting window, or nutrient is known to interact with the peptide itself; correcting deficiencies precedes judging response.
Exercise: Indirect and potentiating. Aerobic exercise transiently raises scalp blood flow, the same variable this ingredient is marketed on, so the two are plausibly complementary. Practically, sweat and post-workout washing strip a leave-on serum, so application after showering rather than before training preserves it.
Stress management: Indirect. Sustained psychological stress precipitates telogen effluvium (a diffuse temporary shedding) that no topical peptide addresses, and heightened scalp neuropeptide tone may amplify the irritation this product can cause. Lowering stress load protects the outcome being measured rather than modifying the ingredient.

Monitoring Protocol & Defining Success

No biomarker tracks this ingredient itself, so monitoring serves two purposes: excluding the correctable causes of hair loss that would otherwise be mistaken for non-response, and measuring the hair outcome directly. Baseline testing consists of the panel below, drawn before the first application, together with standardised photography of a fixed 1 cm² area at the vertex under identical lighting, camera distance, and parting. Ongoing monitoring follows a set cadence: photography repeats at 12 weeks and 24 weeks, then every six months; the laboratory panel repeats at six months, or sooner if shedding increases, and annually thereafter once values sit in range. Success is a measurable rise in hair count or shaft calibre at the fixed site by 24 weeks, not a subjective impression of fullness, which drifts with lighting, haircut, and expectation.

Biomarker	Optimal Functional Range	Why Measure It?	Context/Notes
Ferritin	70–100 ng/mL	Iron stores gate hair shaft production	Conventional lower limit is only 15–30 ng/mL; ferritin rises with inflammation, so it is paired with hs-CRP (high-sensitivity C-reactive protein, a general marker of inflammation)
25-hydroxyvitamin D	40–60 ng/mL	Low status tracks with diffuse shedding	Conventional sufficiency threshold is ≥30 ng/mL; no fasting needed; retested after three months of correction
TSH	0.5–2.0 mIU/L	Thyroid dysfunction causes diffuse hair loss	TSH (thyroid-stimulating hormone, the pituitary signal setting thyroid output); conventional range extends to 4.5 mIU/L; drawn in the morning and paired with free T4 (free thyroxine, the main circulating thyroid hormone)
Serum zinc	90–130 µg/dL	Deficiency impairs follicular keratin synthesis	Fasting morning draw; zinc supplements withheld for 24 hours; samples with ruptured red cells read falsely high
hs-CRP	<1.0 mg/L	Flags inflammation that both suppresses growth and predicts stinging	Fasting not required; testing deferred for two weeks after any infection
Complete blood count with haemoglobin	Haemoglobin 13.5–15.0 g/dL (women), 14.5–16.0 g/dL (men)	Anaemia produces diffuse shedding that mimics non-response	Best drawn with ferritin on the same sample
Free and total testosterone, DHEA-S	Mid-reference for age and sex	Androgen excess in women drives pattern loss the serum cannot offset	DHEA-S (dehydroepiandrosterone sulfate, an adrenal androgen precursor); drawn days 3–5 of the cycle in menstruating women, morning sample
Hair count and shaft diameter at a fixed 1 cm² vertex site	No established target exists; the measure tracked is change from the individual’s own baseline	The only direct measure of the outcome being purchased	Standardised photography or phototrichogram (a magnified hair-counting image); same operator, lighting, and parting at each visit

Alongside the laboratory panel, these qualitative markers are tracked:

Shedding volume, counted as hairs collected in the shower drain over a fixed washing routine
Scalp comfort, specifically itch, stinging, tightness, and flaking during the first two weeks
Perceived hair body and styling hold, which changes with shaft calibre before density visibly changes
Width of the midline part and the size of the visible scalp show under overhead light
Any lightening of new growth at the roots, which would signal the pigmentation concern
Adherence, recorded as missed application days per month, since the commonest cause of apparent failure is inconsistent use

Emerging Research

Head-to-head peptide serum trial: NCT07536100 is a randomised, triple-masked 80-participant study at Thailand’s Institute of Dermatology comparing a peptide factor hair serum with 2% minoxidil over 24 weeks, with hair count in a 1 cm² vertex area as the primary endpoint. It would give the category its first active comparator.
Withdrawn device-assisted trial: NCT04882969, a Montefiore pilot pairing a 1927 nm thulium laser with the serum containing this ingredient, was withdrawn with zero participants enrolled. Its collapse is why no registered trial has ever measured an outcome for a named sh-Polypeptide-71 product.
Completed null trial: NCT04554732 tested a growth-factor hair serum against chemotherapy-induced hair loss; none of twenty evaluable patients achieved meaningful hair preservation (Mann et al., 2026). It weakens the case that topical growth-factor peptides protect follicles under stress.
Immune-privilege guardian hypothesis: Bertolini et al., 2016 proposed VIP receptor stimulation as a way to halt progression of alopecia areata lesions. A controlled test in that condition would be the strongest possible evidence for the ingredient’s core mechanism.
Pigmentation counter-signal: Gomez et al., 2025 identified VIP as a negative regulator of human hair follicle pigmentation. Whether daily scalp exposure lightens regrowing hair is unstudied, and a positive finding would materially weaken the case for long-term use.
Device-assisted delivery: A systematic review and meta-analysis by Abdi et al., 2023 found microneedling amplifies the response to a topical agent in pattern hair loss. Whether that extends to a molecule of roughly 3,300 daltons, or only to small molecules, is unresolved.

Conclusion

sh-Polypeptide-71 is a laboratory-made copy of a natural human nerve messenger, sold as one component of expensive multi-ingredient scalp serums for thinning hair. The reasoning behind it is coherent: the natural molecule is released by nerve fibres wrapped around hair roots, it widens small blood vessels, it prompts skin cells to multiply and move, and in isolated human hair roots it helps hold off immune attack. Each of those observations comes from cell culture or from hair roots kept alive in a dish.

What does not exist is human evidence. No study naming this ingredient appears in the medical literature at all, no controlled study has measured hair counts for any product identified by it, and the favourable reports in circulation come from the company that sells the serum and from a trade journal whose readership performs and sells the associated procedures. The one independent trial of a comparable growth-factor serum found nothing. Working against it, the same messenger suppresses pigment production in human hair roots and amplifies inflammatory signals in irritated skin.

For someone already using treatments backed by real outcome data, adding this ingredient is plausibly harmless and plainly unproven, at roughly a hundred dollars a month before clinic sessions. The distance between how it is said to work and what has been shown in people is unusually wide.

Top - Benefits - Risks - Protocol

sh-Polypeptide-71 for Hair Regrowth

Motivation

Recommended Reading

Grokipedia

Examine

ConsumerLab

Systematic Reviews

Mechanism of Action

Historical Context & Evolution

Expected Benefits

High 🟩 🟩 🟩

Medium 🟩 🟩

Low 🟩

Increased Hair Density and Shaft Diameter Within Multi-Peptide Scalp Serums ⚠️ Conflicted

Speculative 🟨

Improved Blood Supply Around the Follicle

Protection of Hair Follicle Immune Privilege

Follicular Keratinocyte Proliferation

Reduced Scalp Inflammation and Flaking

Benefit-Modifying Factors

Potential Risks & Side Effects

High 🟥 🟥 🟥

Medium 🟥 🟥

Low 🟥

Application-Site Irritation and Contact Sensitisation

Vasoactive Effects at Systemic Exposure

Speculative 🟨

Loss of Hair Shaft Pigmentation

Amplified Cutaneous Inflammatory Signalling

Angiogenic Stimulation of Undiagnosed Scalp Lesions

Risk-Modifying Factors

Key Interactions & Contraindications

Risk Mitigation Strategies

Therapeutic Protocol

Discontinuation & Cycling

Sourcing and Quality

Practical Considerations

Interaction with Foundational Habits

Monitoring Protocol & Defining Success

Emerging Research

Conclusion