The drug, which in its earliest, unsexiest incarnation existed solely as a glaucoma treatment, is best known as the U.S. Food and Drug Administration-approved wonder drug that can grow and darken your poor listless lashes . Now, it's being tested for a new use: growing hair on your dome.

No one tracks just how many doctors across the country are using Latisse off-label to target hair loss, but Dr. Alan Bauman, a Boca Raton, Fla., board-certified hair restoration physician has been using the drug this way for about three years, beginning around the time the FDA approved it for eyelash growth in December 2008. He describes his own personal "eureka!" moment:

"Patients who were using it for eyelashes sometimes have eyebrow problems, so it’s a short hop to the eyebrows," he explains. "So, of course, if it was working there, too — from the eyebrows, it’s just a short hop to the hairline."

Allergen, the health care company that manufactures the eyelash enhancer, is currently testing the safety and efficacy of a new formulation of bimatoprost, the active pharmaceutical ingredient in Latisse, in growing hair on the scalp, says Heather Katt, a spokeswoman for Allergen.

The appeal of using Latisse for hair loss is its ease and convenience, as it seems to only require one drop to the affected area once a day; minoxidil (better known as Rogaine) requires two, and Propecia requires daily pill taking.

Bauman says he sees about 1,000 new hair loss patients each year, about 700 of which end up on some kind of medical management — and so far, he's only used Latisse on a "couple dozen" patients, usually those who are allergic to the usual treatments, which is what happened to 70-year-old Rhoda Kelly.

Kelly's hair was thinning a bit on the back of her head, so she tried Rogaine, but suffered a bad allergic reaction. So Bauman suggested she try Latisse.

Kelly started to see noticeable results about four months after starting Latisse, as her thin hair started to grow in thicker. Now, 14 months later, Kelly says, "My hair is in much better condition — it looks healthy." She's still using Latisse, combined with "a slew of other vitamins," including a pharmaceutical-grade biotin and a marine-derived protein-polysaccaride, and a protective sun hat.

 
Courtesy of Dr. Alan Bauman
On the left is a photo of Rhoda Kelly's hair before using Latisse, which had started to thin a bit. On the right, Kelly's hair is thicker after using Latisse daily.

Kelly, by the way, has strawberry blonde hair, which has gotten lighter after years in the Florida sun. It hasn't darkened after using Latisse. When Latisse first hit the market, much ado was made about one of the more surprising risks: In rare cases, it could cause light eyes to turn brown. Bauman says he hasn't seen any evidence that this applies to hair, or the skin on the scalp, for that matter.

The major drawback: It's expensive. Each 2-ounce bottle costs $100 to $150 — and some patients will run through two or three bottles a month, Bauman says.

"Expense is a big disadvantage, but perhaps the biggest problem with this technology is that it does not restart hair growth for hair that has stopped growing," points out Perry Romanowski, a cosmetic chemist and one of the brains behind the popular beauty blog, The Beauty Brains. "If it works on scalp hair at all (and this hasn't been definitively proven), it will only be able to thicken existing, working hair follicles."

Basically: If you already have a bald patch, Latisse can't help you there.

"Since what people really want from this product is something that will bring their hair back, I suspect that they will be disappointed because that will not happen," Romanowski says. "Are a few thicker, fuller strands going to be worth the expense? Perhaps to some people."