The US Food and Drug Administration (FDA) has approved a new prescription drug, Latisse, for lengthening eyelashes. The active ingredient in the drug was first used to treat glaucoma. Then the manufacturer, Allergan, realized that one of the side effects, eyelash growth, was marketable. From Scientific American:
The med... should be available by March from a doctor or with a prescription from one. Price tag: $120 for a month’s supply. According to manufacturer Allergan, the drug usually nets results two to four months after users start it. Potential side effects: Some 4 percent of users experience eye itching and redness, and it may also temporarily darken the skin of the eyelid, according to the company...New eyelash-lengthening drug approved
It's not clear exactly why Latisse promotes eyelash growth, but the company speculates that the drug may increase the length and amount of hair that sprouts during the growth cycle. It’s possible that the drug may also spur eyebrow and scalp hair growth, doctors told the Wall Street Journal. But Allergan spokesperson Heather Katt says the company hasn't explored using Latisse for those purposes.