A laboratory-made fragment of a thymus messenger, sold as a firming and renewal ingredient for skin and scalp products. The case rests mainly on cultured skin cells and testing run by the company that sells the raw material. No independent published study has measured facial firmness, elasticity or lines with it as the only thing changed. Inexpensive, low-risk, unresolved. (Full Review)

Protocol

Standard regimen

2% peptide solution, twice daily

Cream or serum on clean facial skin for at least 56 days

Formulation requirements

pH 5.0–8.0

Water phase of cold formulations, or below 40 °C once an emulsion has formed; supplier solution is preservative-free

Best time of day

Morning and evening

Morning pairs with sun protection; evening avoids low-pH acids and benzoyl peroxide

Time to effect

Facial firmness

56 days

The manufacturer's endpoints were measured at 56 days of twice-daily use

Hair shedding

Weeks 4 to 8

The hair trial saw separation at weeks 4 to 8

Earliest valid read

8 weeks

Anything judged before 8 weeks reflects hydration from the vehicle, not matrix change

Benefits

Low: Improved facial firmness and elasticity; reduced hair shedding in acute telogen effluvium, not central to skin rejuvenation

Speculative: Increased keratinocyte stiffness and cytoskeletal remodelling; elastic-fibre assembly via fibulin-5 and lysyl oxidase-like 1; epidermal renewal and local immune signalling

Contraindications

Positive patch test to the peptide or any component of the finished formula (absolute contraindication)

Skin within 72 hours of an ablative laser, medium-depth peel or microneedling, or any wound before re-epithelialization

Active, weeping or fissured dermatitis at the application site, until the barrier has healed

Direct periocular use of any product not ophthalmologist-tested for the eye area

Pregnancy and lactation for products intended for large body-surface application

Key Interactions

Prescription topical retinoids (tretinoin, adapalene, tazarotene)

Topical corticosteroids (hydrocortisone, mometasone, clobetasol)

Over-the-counter benzoyl peroxide

Over-the-counter exfoliating acids (glycolic, lactic, salicylic)

Oral collagen peptides, hyaluronic acid, vitamin C (no caution required)

Risk & Side Effects

Low: Allergic contact dermatitis to the finished product; irritation and sensitization on a compromised barrier; displacement of better-documented actives

Speculative: Unintended immune modulation; systemic absorption

Monitoring

Marker	Target	Why
Skin elasticity (cutometer R2)	No established universal target; a rise from own baseline exceeding the device's repeat-measure variation	The endpoint the firmness claim rests on
Transepidermal water loss (TEWL)	10–20 g/m²/h on facial skin	Detects barrier disruption before visible irritation
Stratum corneum hydration (corneometer, arbitrary units)	Above 45 arbitrary units on the cheek	Separates vehicle hydration from genuine matrix change
Standardized photography and wrinkle grading	No numeric target; improvement in matched images at 8 and 12 weeks	The outcome that actually matters to the user
Skin surface pH	4.5–5.5	An acid mantle outside this range signals barrier stress from the routine
Patch test, if a reaction occurs	Negative to all components	Identifies the responsible allergen rather than blaming the peptide

Cadence: Week 4 for tolerance only, then weeks 8 and 12 for effect, then every 6 months if continued

Qualitative Assessment

How makeup sits across the cheek and jawline by late afternoon
Morning puffiness and how quickly it settles
Any stinging, tightness or warmth in the first 10 minutes after application
Subjective firmness on waking, recorded the same way each week
Whether other people notice a change without being prompted

Acetyl Tetrapeptide-2 for Skin Rejuvenation

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment