The Scientist: Ellen Marmur, M.D., a New York-based dermatologist

The Answer: Yes, eyelashes can and do go gray. But they tend to do it later than the hairs on your head, so you could enjoy dark lashes for decades longer.

The stem cells in the hair follicle—whether on your head, your body or eyelids—can only generate so much melanin pigment throughout their lifetimes. Therefore, their ability to imbue hair with color wanes as we get older. When the cells can only produce half as much melanin as they used to, that’s when hair looks gray. When they lose all their melanin, hair looks white. That’s why hair tends to go from dark to gray to white, in irreversible stages. (There are exceptions, including the case of alopecia areata, in which eyelashes and circles of hair on the head fall out and then grow back in temporarily gray.)

Eyelashes, small as they appear, are typically thicker and coarser than the hair on our heads, and unless you’re a very fair blonde or redhead, they are typically dark, with a good deal of brown pigment in the mix. These higher caliber hairs are more robust and therefore stave off graying for longer. The same goes for other coarse body hair, such as pubic and underarm hair.

While many women may notice their eyelashes becoming thinner, finer and fewer in number once they hit their 40s, it may not be until their reach their 70s when they start to see changes in pigment. And that’s where mascara comes in. Darken and thicken aging lashes with a thick-brushed mascara with plumping fibers, but steer clear of waterproof formulas that can be harsh on vulnerable hair. Most importantly, be choosy about how you take your mascara off, and use only gentle, oil-based makeup removers.

MORE: Take the Eye Makeup Quiz to Get Your Personalized Lash Advice