A lab-made copy of a natural growth signal applied to the scalp to coax resting hairs into growing. Lab and animal work is strong, but human proof it regrows hair is essentially absent, largely because the delicate protein barely passes through intact skin. Tolerability appears good; most evidence comes from product sellers. (Full Review)

Protocol

Application

Few drops once–twice daily

To clean, dry thinning areas; massaged in and left on

Enhanced delivery

Microneedling or fractional laser

Periodic schedule (often weekly to monthly) to drive the protein into the skin

Form

Multi-growth-factor blend

Almost always one component of a blend rather than a standalone product

Time to effect

Visible change

3–6 months

Plausible timeline by analogy; no change by then suggests non-response

Benefits

Low: Promotion of the hair growth phase; improved follicle blood supply

Speculative: Support of hair density when combined with other actives; improved hair-shaft quality and caliber

Contraindications

Current or recent scalp skin cancer or pre-cancerous lesions

Active scalp infection or open wounds

Active chemotherapy or radiation (without oncology direction)

Pregnancy and breastfeeding

Key Interactions

Topical scalp irritants and retinoids (high-strength exfoliating acids)

Minoxidil and other topical hair actives

Microneedling and energy-based devices (fractional lasers, radiofrequency)

Risk & Side Effects

Low: Local skin and scalp irritation; local effects known from medical use of bFGF

Speculative: Theoretical stimulation of unwanted cell growth; effects from compromised skin-barrier application

Monitoring

Marker	Target	Why
Ferritin (iron stores)	50–100 ng/mL	Low iron stores drive diffuse hair shedding and blunt regrowth
Vitamin D (25-hydroxy)	40–60 ng/mL	Deficiency is linked to hair-cycle disruption
TSH	1.0–2.0 mIU/L	Thyroid imbalance causes reversible hair loss that can confound results
Free testosterone & DHEA-S	Sex- and age-appropriate optimal range	Androgen excess underlies pattern loss this peptide does not address
Zinc (serum)	90–110 µg/dL	Deficiency impairs follicle keratin production

Cadence: Baseline, 3 months, and 6 months, then every 6 months thereafter

Qualitative Assessment

Reduced daily hair shedding (fewer hairs on pillow, in shower, or on brush)
Visibly increased density or coverage in previously thinning areas
Improved hair-shaft thickness or texture
Absence of scalp irritation, indicating good tolerability
Subjective confidence in appearance, the practical endpoint for cosmetic use

Sh-Polypeptide-1 for Hair Regrowth

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment