Health & Fitness | July 23, 2017 5:00 am

Experimental Cancer Drug Is Inexplicably Reversing Men’s Gray Hair

Unexpected side effect baffles doctors, but could be sign of treatment's efficacy.

Male cancer patients are experiencing a previously unseen reaction to their medication: their gray hair is turning youthfully dark.

Though chemotherapy is usually known for making hair fall out, 14 lung cancer patients in a Spanish study found that the drug began to restore their hair pigment. They were being treated with new immunotherapy drugs that work differently and therefore could have different side effects. So far, doctors are unsure why the pigment restoration is happening.

Hair darkening might be a indirect indication that the drugs are working, because all but one of the patients with the newly-darkened hair responded better to treatment than other patients in the study.

However, researchers say more research is needed to show that these results aren’t a fluke and to figure out why exactly the drugs might change hair color.