FAQs Q: What causes keratosis pilaris? A: Our skin produces a protein called keratin that constructs 90% of the outer-most layer of the skin protecting the skin from infections and other harmful environmental stressors. Keratosis pilaris is caused by the overproduction and buildup of keratin which further plugs pores and blocks the opening of hair follicles. Researchers have yet to uncover exactly what triggers the build up. Q: Where does keratosis pilaris occur? A: According to one study; most commonly found on upper arms (92%) followed by thighs (59%) and buttocks (30%) Q: Can keratosis pilaris appear suddenly? A: Depending on one’s age current skin issues and time of year keratosis pilaris can appear suddenly or rapidly progress. Since keratosis pilaris most commonly occurs in adolescents (usually after age 10) keratosis pilaris can get worse at puberty. Additionally keratosis pilaris is present more often with eczema or dry skin and often gets worse in cold dry weather. Adults can develop keratosis pilaris as well and experience flare ups in tandem with other skin conditions and/or during the winter months.