毛囊角化症（Keratosis pilaris），无炎性反应者又称毛周角化症，俗称鸡皮病，常被误以为是痤疮或是皮肤卫生清洗不干净，实则是一种无法根治的常染色体遗传性疾病。该病在幼儿期病例较少或病症不明显，但青春期阶段呈高发态势，后随着年龄增长而逐渐减轻直至消失。特点是症状冬季严重，夏季减缓。

临床上，约40%至80%的青少年均会出现不同程度的毛囊角化问题，大部份更在10岁或之前便已出现征状。

Keratosis pilaris (KP) (also follicular keratosis, lichen pilaris, or colloquially "chicken skin") is a common, autosomal dominant, genetic follicular condition characterized by the appearance of rough, slightly red bumps on light skin and brown bumps on darker skin. It most often appears on the back, outer sides of the upper arm (though the forearm can also be affected), face, thighs, and buttocks; KP can also occur on the hands, and tops of legs, sides, or any body part except glabrous skin (like the palms or soles of feet). Often the lesions will appear on the face, which may be mistaken for acne.