Erythema consists of macules and papules that form when the skin becomes congested, and is the most common symptom of skin diseases, such as hives, macules and papules of acute eczema, rosacea, and viral or bacterial infections. In terms of location, rashes can appear on various parts of the body, such as the face, limbs, abdomen, and scalp. In terms of morphology, rashes are mainly categorized as macules, papules, pimples, hives, and roseola. In terms of causes, rashes can be caused by allergic diseases, bacterial infections, viral infections, and skin inflammation caused by mosquito bites. In terms of accompanying symptoms, rashes are usually accompanied by itching, pain, and even flaking and fever. For rashes on the surface of the skin, it is important to go to the dermatology department of a regular hospital in a timely manner.