"In adolescents, we see blackheads, white-heads, and little surface pimples, usually along the forehead and nose, where the oily T zone is," explains Diane Berson, an assistant professor of dermatology at the Weill Medical College of Cornell University, in New York City. "In adult women, breakouts tend to be on the lower half of the face." And these spots are often larger, more inflamed, and more painful. "It's hard to say why adult acne manifests itself differently, although it has to do with different hormones," says Keri. Even worse, blemishes take longer to abate and disappear. "Since adult pimples get darker than teen pimples, the discoloration from one can last for three or four weeks," says Marianne O'Donoghue, an associate professor of dermatology at Rush University Medical Center, in Chicago.