Dermatitis is a general term for acute and chronic inflammatory reactions of the skin caused by various causes. For example, in contact dermatitis, the trigger is exposure to exogenous substances. When the exogenous substance is a primary irritant, the onset is rapid and may be accompanied by burning and stinging sensations in addition to itching, while when the exogenous substance is a contact sensitizer, the onset is somewhat delayed and the stinging symptoms are relatively mild compared to the primary irritant. In terms of location, dermatitis in thin and tender areas of the skin starts with flushing and itching, which may be aggravated by blistering, erosion, and exudation, while dermatitis in thick keratinous areas usually has keratinous hyperplasia, cracking, and flaking as concomitant symptoms of itching. As for the course of the disease, acute onset of dermatitis is usually rapid, and the progression of the disease is often accompanied by flushing, edema and inflammatory exudate tendency, while chronic onset of dermatitis is usually accompanied by significant infiltration and hypertrophic hyperplasia tendency along with pruritus. In addition, dermatitis with exogenous triggers is often limited in its onset, while dermatitis with endogenous triggers has a clear tendency to symmetrical onset and generalized spread.