Abnormal thickening of the stratum corneum is one explanation for hyperkeratosis, and another explanation is a pathological change in which the epithelial cells on the surface of the skin or mucous membranes become hyperkeratotic and the stratum corneum becomes inflamed and thickened. The following is a detailed description of the etiology. The true cause of the disease is not known, although most literature suggests that it has a genetic predisposition (commonly seen in patients with ichthyosis) and occurs more often in people with allergic or atopic constitutions, or in people with nutritional deficiencies (especially those with vitamin A deficiency); it may also occur more often when combined with low humidity and dry air in the environment, as well as certain irritants such as tar and oil. Keratosis pilaris is a genetically predisposed body type. Some experts say that people with this constitution have a thickening of the keratin around the hair follicles, resulting in the mouth of the follicles being clogged with too much keratin, causing small bumps in a grain. Some patients with atopic dermatitis and ichthyosis usually also suffer from keratosis pilaris. The symptoms are more severe in winter because they are related to keratinization of the pores and thickening of the keratin, so when the climate is dry and cold, the thickening of the keratin will be aggravated and the symptoms will become more obvious. In addition to congenital factors, it has also been reported that it is related to vitamin A deficiency. Vitamin A deficiency causes systemic dryness, and dryness exacerbates the symptoms of keratinized pores.