Causes of Keratosis Pilaris
Keratosis pilaris occurs when dead skin cells clog the hair follicles (also called pores) in your skin. It is not caused by a fungus, bacteria, or a virus. It is not contagious. It occurs more often during the winter months when the air is dry. It tends to improve in warmer months when humidity is higher.

Keratosis pilaris can occur at any age and affect anyone. It usually appears before age 2 or during the teenage years. It can worsen during pregnancy and after childbirth. It generally affects women more often than men. Keratosis pilaris may disappear or improve with age.

You are more likely to develop keratosis pilaris if you have:

A family history of it.
Asthma
Dry skin.
Eczema (also called atopic dermatitis).
Excess body weight.
Hay fever.