What it is

Thymosin beta-4 is a naturally occurring 43-amino-acid peptide, found in some follicle cells during the hair cycle. It has no approved hair use. Products labelled TB-500 are sold as research chemicals; they are unapproved and we found no human hair data for them.

How it works

In rodents it increased migration and differentiation of follicle stem-cell-like cells and raised an enzyme that remodels the surrounding tissue (Philp 2004). Mice engineered to overproduce it regrew hair faster after hair removal and knockouts were slower (Gao 2015).

What the studies show

Thymosin beta-4 stimulated hair growth and stem cell migration in rats and mice (Philp 2004).
Overexpression sped regrowth in transgenic mice and deletion slowed it (Gao 2015).
A PubMed search for human hair studies returned only animal work and reviews.

Side effects and safety

Unknown for hair use. Injectable peptides from unregulated sources carry contamination and dosing risks.

Bottom line

Interesting biology, but no basis for self-injecting peptide products. Discuss with a doctor.

Studies 2

Philp D et al. Thymosin beta4 increases hair growth by activation of hair follicle stem cells. FASEB J. 2004

Design: animal
Who: rats, mice and rat follicle cells

Tested: thymosin beta-4

Result: Stimulated hair growth and stem cell migration in rodents.

Read the study ↗

Gao X et al. Thymosin beta-4 induces mouse hair growth. PLoS One. 2015

Design: animal
Who: transgenic and knockout mice

Tested: thymosin beta-4 overexpression or deletion

Result: Overexpression sped regrowth after depilation and knockout slowed it.