Heat rash is the common name for the clinical condition “prickly heat”, which is a superficial inflammatory skin disease that occurs in summer or in hot environments where sweat overflows. Eczema is a non-infectious inflammatory skin disease caused by a variety of internal and external factors, with intense itching and a polymorphic, often symmetrical rash. There are significant differences between the two diseases in terms of causative factors, prevalent sites and clinical symptoms, and they are generally not difficult to distinguish. The cause of “heat rash” is relatively simple. In a hot and muggy environment, the sweat evaporates slowly and the sweat stagnates in the sweat ducts, increasing the pressure, leading to acute inflammation of the surrounding tissues due to rupture of the sweat ducts and extravasation of sweat in severe cases, so the rash is mostly limited to sweat overflow and hot and humid areas of skin folds. The occurrence of “eczema” is mostly mediated by allergic reactions, and there is a clear basis for endogenous susceptibility, in addition to external factors that induce it. In layman’s terms, patients with eczema tend to be allergic, and eczema itself is an “inside-out” disease, so both sides of the body are susceptible to symmetrical rashes due to an intrinsic basis of reciprocity. In terms of symptoms and course, “heat rash” is commonly known as “white heat rash” and “red heat rash”, in which white heat rash has no obvious conscious symptoms and sheds The red prickly heat rash is accompanied by itching and stinging sensation, and the course of the disease is shorter, leaving a light flaking after the lesions fade. In contrast, eczema has a chronic course and is prone to recurrence. In addition to itching, the degree of inflammatory response is characterized by dynamic evolution, and can be divided into three categories: acute eczema, subacute eczema, and chronic eczema. Any one type can develop and evolve to other types. Therefore, the clinical lesion pattern is diverse. In the acute phase, the rash develops rapidly, the inflammatory response is heavy, tissue edema is evident, and a large amount of plasmacytic exudate is likely to occur. In contrast, in the chronic phase or chronic onset, eczema lesions develop slowly and show a marked tendency to hyperplasia, hypertrophy, and infiltration.