The NPD Group, a market research firm, reports that use of makeup is falling among teenagers and women age 18 and up. While young girls are becoming exposed to beauty routines earlier on, the report says, excitement might be wearing off by the time older girls are establishing their own regimen, observes NPD beauty-industry analyst Karen Grant.

Grant says that overall, girls in the 13- to 17-year-old range still use more makeup than their younger sisters, but the percentage of the high schoolers using makeup now is less than it was a few years ago, while the percentage of elementary and middle-school girls is higher.

By age 18, these young women are looking to keep their skin healthy and enhance their appearance with a handful of tried-and-true cosmetics, Grant explains, but their experimental phase is largely over.

“You’ve got girls asking, ‘Do I really need this?'” says Grant. “Maybe it’s not that exciting anymore because they’ve been using it since they were younger.”

Lip products is the most used cosmetic category across all ages, says Grant, with younger girls using balm, tweens and teens using gloss and then adults wearing lipstick. But mascara is the second most important category for teenagers–replacing all the bath washes and gels that younger girls like–and women largely have a commitment to using mascara through their mid-60s.

Among 8- to 12-year-olds, 18 percent are wearing mascara on a regular basis; 47 percent of 13 to 17-year-olds; and 56 percent by age 18, according to Grant.

Compared to 2007 levels, that is an 8 percent increase in usage of mascara by tweens, while lipstick had a 5 percent increase. Both products saw a drop in usage, though, among 13- to 17-year-olds from three years ago.