Your scalp produces tons of pure oils—this can be a good factor, as sebum is what retains your strands shiny and moisturized. It’s when your scalp accrues an excessive amount of oil that turns into a slight subject, buildup, flakes, and greasy hair not too far behind. The precise timestamp seems completely different for every particular person, however for straight-to-wavy hair types (assume pin-straight to free bends), the hair tends to get oily quicker, as it is simple for sebum to journey from root to shaft (it’s additionally why folks with this hair sort might must shampoo more often). 

Right here’s the place your brush of choice comes into play: Brushing quickens the journey fairly a bit—the bristles can switch the oil from the scalp all the way down to the strands. “Brushing your hair whereas it’s dry or working your fingers via your hair strikes the oil down the hair shaft which might make hair look extra oily,” says hairstylist Franck Izquierdo, co-founder of IGK Hair Care. To not point out, the oils in your fingertips can introduce much more grease to the strands themselves, however that’s an entire different dialogue. 

Many additionally declare that combing on the roots can stimulate the follicles up prime (like a mini scalp massage), which might result in extra oil manufacturing, and, thus, a greasier mane. “There are theories that brushing the hair can stimulate the scalp’s oil glands, although I’ve not seen knowledge proving that to be the case,” says board-certified dermatologist Iris Rubin, M.D., founding father of SEEN Hair Care. It’s not out of the query, however the oil-transferring course of above is the probably perpetrator.