sh-Polypeptide-4 for Hair Regrowth - Quick Reference Sheet
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sh-Polypeptide-4 for Hair Regrowth

Created on 08/25/2026 – Quick Reference based on Evidence Review created using AI4L / Grok 4.5 – Audit

Laboratory-made stem cell factor is a biologically interesting add-on with a pigment-cell rationale, but no published trial has counted scalp hairs after leave-on use. Injected pharmaceutical doses caused hive-like reactions and extra pigment cells. A protein this size has little unaided reason to cross intact skin. It is not a stand-in for treatments that have hair-count trials. (Full Review)

Protocol

No established hair-density protocol
Leave-on serum, once or twice daily
On a dry scalp; no named clinic regimen with hair counts
Timing
Once-daily evening
Typical so the film stays put; topical follicular half-life unknown
Cosmetic concentrations are undisclosed
Not in micrograms per milliliter
INCI lists presence only; hematology 5–20 µg/kg subcutaneously is a different route, not a hair dose
Time to effect
Hair and cutaneous pigment-cell support
14 days
Injection-site darkening; a pigment rather than a density timeline
Increased scalp hair density
3–6 months
Hair-cycle endpoints; no trial has counted scalp hairs after topical use

Benefits

Contraindications
  • KIT inhibitors (imatinib, sunitinib, barzolvolimab)
  • Systemic mastocytosis, recurrent anaphylaxis, or poorly controlled chronic urticaria
  • Active cutaneous melanoma or numerous atypical melanocytic lesions on the intended field
  • Known hypersensitivity to E. coli-derived proteins or to ancestim
  • Pregnancy and lactation
  • Open, infected, or highly inflamed scalp until the barrier is intact
    •
Key Interactions
  • Mast-cell secretagogues (opioids such as morphine, nonsteroidal anti-inflammatory drugs, vancomycin, radiocontrast)
  • Histamine type 1 and 2 blockers (H1/H2 antihistamines: cetirizine, famotidine)
  • Other hair-growth actives (minoxidil, finasteride, dutasteride)
  • Other topical growth-factor analogues (VEGF, keratinocyte growth factor, IGF-1 copies)
  • Microneedling or ablative lasers
    •

Risk & Side Effects

  • High: Mast-cell degranulation with wheal-and-flare and anaphylactoid reactions
    •
  • Medium:
  • Low: Unwanted cutaneous hyperpigmentation
    •
  • Speculative: Promotion of KIT-driven cell clones; Immunogenicity of E. coli recombinant protein
    •

Monitoring

Marker Target Why
Hair density (phototrichogram) Rise versus own baseline; no universal target Objective hairs per area
Hair shaft diameter Rise versus own baseline Tracks miniaturization
Global scalp photography Documented change versus baseline Real-world appearance
Serum tryptase Stay at personal baseline Mast-cell burden if atopy or non-topical use

Cadence: Baseline; about 12 and 24 weeks, then every 6 months if still in a stack. Monthly for shed-hair, itch or wheals, and darkening.

Qualitative Assessment

  • Shed-hair counts on pillow or drain versus the person’s pre-trial week
  • Local itch, wheal, or flushing after application (mast-cell warning)
  • New or expanding dark patches on treated skin
  • Perceived coverage at the part or crown on standardized photos
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.