Researchers have developed a serum that stimulates hair growth in mice by replicating the fatty acid release triggered by skin irritation, without causing discomfort. The treatment, based on monounsaturated fatty acids, shows promise in lab tests on human hair follicles. Scientists plan human trials following encouraging results.
Sung-Jan Lin at National Taiwan University and his colleagues discovered the link between skin irritation and hair growth several years ago during mouse experiments. 'We unexpectedly discovered that, after skin irritation, the size of skin adipocytes [fat cells] quickly shrinks before hair starts to regrow,' says Lin. They speculated that adipocytes release fatty acids via lipolysis to fuel hair regrowth.
To investigate, the team induced eczema on shaved mice by applying an irritating compound to their backs. Within 10 days, hair follicles in these areas entered an active growth phase, showing visible hair regrowth. This did not occur in untreated shaved areas or mice without eczema. Macrophages, immune cells, migrated to the skin's fat layer, signaling fat cells to release fatty acids. These were absorbed by hair follicle stem cells, boosting mitochondria production for energy and promoting growth. This process aligns with prior research showing plucking hair triggers immune signals for nearby follicle growth.
Eczema does not typically promote hair growth in humans, but other irritations, like plaster casts on broken limbs, have been linked to excessive hair growth. To test fatty acids without irritation, the researchers applied serums of various fatty acids dissolved in alcohol to shaved mouse skin. 'We found that only monounsaturated fatty acids rich in adipose tissues, such as oleic acids and palmitoleic acids, are effective in promoting hair regeneration when topically applied to skin,' says Lin.
The team has patented the serum and observed promising results on human hair follicles in lab settings. They plan to test dosages on human scalps. Lin notes the fatty acids are naturally derived and safe, adding that he applied them to his thighs for three weeks and saw hair regrowth. Christos Tziotzios at King’s College London cautions that it has not been validated in human skin, as animal models differ in follicular biology. Still, he says the study advances understanding of adipocytes in regeneration and may explain hair growth after microneedling, which punctures the scalp to trigger immune responses.
The findings appear in Cell Metabolism (DOI: 10.1016/j.cmet.2025.09.012).