sh-Polypeptide-4 for Hair Regrowth - Quick Reference Sheet
evipedia.ai ← Back

sh-Polypeptide-4 for Hair Regrowth

Created on 07/08/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 4.8 – Audit

A lab-made copy of stem cell factor added to scalp serums for regrowing and re-coloring hair. The color-support rationale is well founded; hair-count claims rest mainly on animal work. No controlled human trials show a cosmetic serum regrows hair, and the large protein struggles to reach the follicle. Main downsides are local irritation and theoretical pigment changes. (Full Review)

Protocol

Form
Leave-on serum
Applied to a clean, dry scalp, often within a growth-factor blend
Frequency
Once–twice daily
Twice daily is common but not shown to beat once daily
Delivery
Microneedling optional
Boosts penetration of the large protein but raises irritation
Time to effect
First assessment
3–6 months
Minimum consistent use before judging any pigment or hair change

Benefits

Contraindications
  • Personal history of melanoma or many atypical moles on the scalp
  • Mast-cell activation syndrome or systemic mastocytosis
  • Active scalp infection, dermatitis, or open wounds
  • Pregnancy or breastfeeding
    •
Key Interactions
  • c-KIT–blocking tyrosine kinase inhibitors (imatinib, sunitinib, nilotinib)
  • Oral antihistamines
  • Topical hydrocortisone
  • Other growth-factor serums, copper peptides (GHK-Cu), topical minoxidil
  • Microneedling and fractional laser
    •

Risk & Side Effects

  • High:
  • Medium:
  • Low: Local skin irritation and itching
    •
  • Speculative: Unwanted pigmentation changes and pigment-cell overgrowth; melanoma-related pro-growth concern; systemic mast-cell activation; immunogenicity or contamination of recombinant proteins
    •

Monitoring

Marker Target Why
Ferritin 40–70 ng/mL Low iron is a common, correctable cause of shedding
25-hydroxy vitamin D 40–60 ng/mL Low vitamin D is linked to hair-cycle disruption
TSH 0.5–2.5 mIU/L Thyroid imbalance causes diffuse shedding

Cadence: Reassess at 3 and 6 months, then every 6–12 months; repeat labs every 6–12 months if previously abnormal or symptoms persist

Qualitative Assessment

  • Shedding rate trending down
  • Visible density or coverage on consistent, same-lighting photos
  • Hair color at the roots (any slowing of greying)
  • Scalp comfort — no persistent itching, redness, or hives
  • Any new or changing mole on the scalp
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.