Red rashes on children may be prickly heat, especially concentrated in areas that sweat a lot, such as the armpits, neck, and trunk. In addition, it may also be due to viral infection or allergy, viral rash is common in measles, early childhood emergency, rubella, scarlet fever, infectious mononucleosis, etc., allergic rash is common in acute urticaria, contact dermatitis, etc. 1, measles: is caused by measles virus caused by respiratory infection, and then appear brown-red maculopapular rash. The brown-red papules mostly appear after fever, starting from the head and neck and gradually spreading to the extremities and trunk. 2. Early childhood emergency rash: it is caused by human herpes virus type 6 infection, which results in fever and red papules. The red papules will first appear on the chest, back and neck of the affected child and then spread to the face and extremities; 3. Rubella: is an acute respiratory inflammation caused by the rubella virus, manifesting as a mild red rash that can start on the face and expand to the neck, chest and other parts of the body; 4. Scarlet fever: is caused by streptococcal infection resulting in fever and red rash in children with an evenly distributed rash accompanied by itching; 5. Infectious mononucleosis: This is mainly due to EBV infection, which causes lymphocyte proliferation and consequently a polymorphic rash. The rash varies in form, including maculopapular rash, urticaria, erythema nodosum, etc. It is mostly distributed on the trunk and can subside around 3-7; 6. Acute urticaria: It is an acute localized edema reaction of the skin, which is caused by food irritation, drug allergy, infection, etc., resulting in raised skin masses with redness, swelling, itching and fever. If the cause of the disease is clear, the child should stay away from, or stop taking drugs that cause allergies; 7. Contact dermatitis: the skin appears erythema, papules, blisters, and itching after contact with animal fur, pollen, formaldehyde, hair dye and other substances. Steroid cream can be used for treatment to relieve the rash and itching symptoms; 8, Kawasaki disease: the specific cause is not clear, but can be induced by infection, common systemic vascular inflammation, manifested as skin rash, mucous membrane congestion, lymph node enlargement, etc., the rash is mainly distributed in the face, neck, trunk and extremities.