Keratin—a strong protein—is a major component of skin, hair and nails. Keratosis results when excess protein build-up causes various types of growths on the skin. There are several causes, and several different types of lesions.
Most types of keratosis have no identifiable cause, but genetics seem to play a role, according to Dr. Nili N. Alai of MedicineNet.com. For example, 50 to 70 per cent of people affected by keratosis pilaris have a strong family history of the condition. The American Academy of Dermatology notes that genetics also plays a role in sebhorreic keratosis. Keratosis pilaris forms small goosebump-like growths on the upper arms, buttocks and legs. Some people refer to it as "chicken skin." Sebhorreic keratosis causes wart-like growths that can appear anywhere on the body.
Keratin build-up might be linked to other conditions, including allergies, eczema, dermatitis, rhinitis, asthma and ichthyosis vulgaris, according to the Mayo Clinic.
Solar keratosis results from excessive exposure to ultraviolet light either from the sun or tanning beds, according to the Mayo Clinic. This excessive exposure interferes with the normal process of skin cell development, and causes discolouration and excess keratin build-up. These growths often appear as dry patches of skin. UV exposure also might influence development of sebhorreic keratosis.
Keratosis appears to be more frequent in people who have excessively dry or hypersensitive skin.