Botox, one of America’s most commonly used drugs, turned 15-years-old this April. And while the drug is getting older, its users are getting younger.

Botox is a strain of the neurotoxin botulinum toxin, and it’s famously used by many celebrities to reduce wrinkles, sagging skin, and other signs of aging. But while this is the stereotypical use for Botox, it’s actually used for a host of different medical problems — treating overactive sweating, preventing migraines, and controlling involuntary muscle spasms. Botox works by paralyzing facial muscles, and its effects last up to six months. Despite its many medical uses, Botox is still most popular as a cosmetic procedure that helps eliminate wrinkles, crows feet, and laugh lines.

For the past decade and a half, women 35 years and older have been the primary users of Botox, often at med spas or dermatology clinics. However, according to the International Spa Association, 56% of millennials have visited a spa within the last year. And thanks in part to a surge of interest from image-conscious millennials, the U.S. spa industry is now worth $16.3 billion. In keeping with that trend, more and more young people are receiving Botox treatments.

However, instead of eliminating wrinkles and other signs of premature aging, these millennials are heading to spas and plastic surgeons nationwide as a way to prevent the first signs of aging.