The growing trend of wearing make-up at the gym or on runs is likely to be causing skin damage, according to scientists based in South Korea and the US.
After testing the effects of applying foundation cream before exercise, the team concluded that it "can reduce skin oil, causing dryness."
"Additionally, make-up can clog pores and increase sebum production," they said, warning in the Journal of Cosmetic Dermatology that people with dry skin are likely to be worst affected by slapping on make-up before working out.
From the University of San Antonio and Korea National University of Education, the researchers said they measured moisture, elasticity, pore, sebum and oil on the skins of 43 male and female students, before and after putting them through a 20-minute run on a treadmill.
After exercising, pores were opened wider on skin that was not covered by make-up, the team found.
"For skin health, it’s best to exercise with your make-up removed," said Dongsun Pak of the Korea National University of Education, whose team carried out the tests due to the "growing trend of individuals wearing cosmetics while participating in physical activities."