What causes keratosis pilaris?

Keratosis pilaris is an inherited skin condition, running strongly in many families, sometimes with a generally dry skin (ichthyosis). The way it is inherited varies from family to family, but often fits into an 'autosomal dominant' pattern – which means that there will be a 1 in 2 chance that each child of an affected parent will inherit the condition. Keratosis pilaris appears when extra keratin accumulates in the hair follicles. This is usually in childhood, and most obvious during adolescence, often it clears in adulthood. It tends to be better in the summer than in the winter. Keratosis pilaris is harmless, and is not infectious.