TLDR Sophora flavescens extract may help hair grow by affecting growth factors and blocking a hair-related enzyme.
In 2002, a study found that Sophora flavescens extract promoted hair growth in C57BL/6 mice by inducing an earlier transition from the telogen to anagen phase in the hair cycle. The extract did not affect the growth of cultured dermal papilla cells in vitro but did increase mRNA levels of growth factors like IGF-1 and KGF in these cells. Additionally, the extract inhibited type II 5α-reductase activity, which is linked to hair growth and androgenetic alopecia. These results indicate that Sophora flavescens extract could be effective in promoting hair growth, potentially through the regulation of growth factors and inhibition of 5α-reductase. The number of subjects used in the study was not provided.
1113 citations
,
August 1999 in “The New England Journal of Medicine” Hair follicle biology advancements may lead to better hair growth disorder treatments.
173 citations
,
July 1995 in “Biochemical and biophysical research communications” Male hormones promote hair cell growth by using a growth factor from nearby skin cells.
94 citations
,
February 1994 in “The journal of investigative dermatology/Journal of investigative dermatology” EGF makes hair follicles grow longer but stops hair production.
385 citations
,
November 1990 in “Journal of Cell Science” Human hair follicles can grow in a lab setting.
November 2021 in “DOAJ (DOAJ: Directory of Open Access Journals)” 
April 2016 in “Journal of Investigative Dermatology” Wnt ligands, produced by dermal papilla cells, are essential for adult hair growth and regeneration.
75 citations
,
October 2002 in “Journal of Dermatological Science” Sophora flavescens extract may help hair grow by affecting growth factors and blocking a hair-related enzyme.
2 citations
,
January 2002 in “The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology” Sophora flavescens extract helps hair grow and prevents acne.
