TLDR Grape seed proanthocyanidins can promote hair growth.
The 1998 study by Takahashi, Kamiya, and Yokoo found that proanthocyanidins from grape seeds significantly increased the proliferation of mouse hair follicle cells by approximately 230% compared to controls. This was part of a larger investigation into natural products for hair growth, examining around 1,000 plant extracts, and suggested that grape seed proanthocyanidins could be a promising natural agent for promoting hair growth.
54 citations,
June 1985 in “American Journal of Dermatopathology” Minoxidil helps grow longer, thicker hair in bald scalps of stumptailed macaques, and early treatment is more effective.
46 citations,
February 1983 in “The Journal of Dermatology” 
45 citations,
November 1979 in “British Journal of Dermatology” Minoxidil causes excessive hair growth in almost all patients.
3 citations,
February 2023 in “ACS omega” Grape seed oil improved hair quality the most, followed by rosehip and safflower seed oils, and reduced damage from shampoo.
January 2020 in “Indian Journal of Pharmaceutical Sciences” Natural products show promise for new hair loss treatments.
19 citations,
January 2010 in “International Journal of Ayurveda Research” Tectona grandis Linn. seeds extract improved hair growth in mice better than minoxidil.
November 2022 in “Cosmetics” Red pigmented rice, like Sang-Yod rice, could help promote hair growth and prevent hair loss.
1 citations,
January 2001 in “Cosmetics and toiletries” Procyanidin B-2 from apple juice significantly increases hair growth and may be more effective than minoxidil without side effects.
