Commonly referred to as "chicken skin", this is a phenomenon of over-keratinization of the skin due to a lack of vitamin A. It occurs most often on the front or outside of the arms and legs. It occurs most often on the front or outside of the arms and legs, and is often mistaken for acne, pimples, or a lack of cleanliness. The most common areas are on the outside of the upper arms, legs, neck, and even the entire back. Some people have darker, rougher skin on the cheeks, which is also called "chicken skin", although the granularity is less obvious. This is due to keratinization at the opening of the sebaceous gland ducts of the hair follicles, forming "keratosis pilaris", which hardens and causes the pores to become occluded. The appearance of small, scattered pimples like pinpoints, flesh-colored, reddish-brown, brown or grayish-black, most of which are painless and itchy. Keratosis pilaris looks very much like "goose bumps", but the general "goose bumps" is due to climate or emotional contraction of the erector spinae muscle, for a temporary skin changes; while the follicular keratosis pilaris is a persistent state of the pimples. "Chicken skin" is not painful, not itchy, not lesions, but particularly dry, flaky, raised areas of dark color, extremely affect the aesthetics.

There are many small bumps on the limbs, very rough, this is very common, especially likely to occur in the upper arms and thighs and calves of the outside, is a skin disease, the scientific name is called keratosis pilaris. It is a hereditary disease.