Keratosis pilaris is caused by a buildup of keratin, the protein that protects skin from infections and other harmful things. The buildup forms a plug that blocks the opening of a hair follicle, but doctors don’t know what triggers the buildup.
If you have dry skin, you’re more likely to have keratosis pilaris. It’s usually worse in the winter months, when there’s less moisture in the air, and then may clear up in the summer.
It often affects people with certain skin conditions, including eczema .
Your doctor can diagnose keratosis pilaris by looking at your skin. You don’t need to be tested for it.