What is the primary characteristic of keratosis pilaris?

Keratosis pilaris is primarily characterized by the appearance of small, rough bumps on the skin, commonly found on the upper arms, thighs, cheeks, and buttocks. These bumps are caused by the buildup of keratin, a protein that protects the skin, which blocks hair follicles. The texture of these bumps can feel like sandpaper and is often most noticeable on the back of the arms.

The other choices do not accurately describe keratosis pilaris. Flaky patches on the cheeks may indicate a different skin condition, such as eczema or psoriasis. Reddish lesions on the legs could be a sign of other issues, such as Folliculitis or different dermatitis. Blisters on the scalp are typically associated with conditions like dermatitis herpetiformis or a contact allergy rather than keratosis pilaris. Thus, the identification of bumps on the back of the arms as the primary characteristic is accurate and aligns with the known presentation of keratosis pilaris.