Q. Is the drug that enhances eyelashes safe to use?
A. In 2008, the FDA approved the prescription drug bimatoprost (Latisse) for treating hypotrichosis (sparse eyelashes), and thus considers it safe and effective for this use. It is a liquid that you apply daily to the base of the upper eyelid. Still, it's hard to recommend a drug solely for such cosmetic purposes, since it does have side effects, and its long-term safety is largely unknown.
Bimatoprost is the same drug as the eye drops used to treat glaucoma (such as Lumigan), which were found to have the unexpected side effect of stimulating eyelash growth. According to the manufacturer, most people will grow longer, darker, and thicker eyelashes, with full effects seen by 16 weeks. If you stop using it, though, your eyelashes will return to their former state.
The potential side effects include red, itchy eyes and darkening of eyelid skin (usually reversible) and of the iris (likely permanent). In addition, if the medication repeatedly drips, hair can grow on the skin around the eyes. A rare side effect that made headlines is the chance that the drug could turn hazel or blue eyes permanently brown. The safety of the drug during pregnancy is unknown, and it should be used cautiously if you already use a similar medication for glaucoma. This video from Consumer Reports shares some other things to know about Latisse before using it.
You should obtain bimatoprost from a physician, who can inform you about side effects and monitor for them. Purchasing it online increases the risk of fakes and expired products.
Because bimatoprost is a cosmetic drug, your insurance company won't cover the cost (about $120 a month). Some mascaras seem to do extraordinary things for eyelashes, too—for a lot less money.
Also see 9 Dangerous Beauty Trends.