The Effect of Topical Minoxidil Treatment on Hair Follicular Growth of Neonatal Hairless Descendants of Mexican Hairless Dogs

In a 1997 study involving eight newborn hairless puppies, descendants of Mexican hairless dogs, daily topical minoxidil treatment was found to stimulate hair growth. After 21 days of treatment, hair growth was observed in the treated areas, with an increase in the number of hairs compared to areas treated only with a vehicle. Histological examination revealed that minoxidil-treated skin contained numerous hair follicles derived from epidermal invaginations, showing various stages of neofolliculogenesis. After 31 days, terminal hair growth was observed. In contrast, areas not treated with minoxidil showed undifferentiated epidermal invaginations. The study concluded that hairless puppies could serve as a useful model for testing hair growth stimulants, and that they respond to minoxidil treatment if applied during the early neonatal phase.