The rash after a fever can be caused by a variety of reasons, so the time for the rash to disappear completely may vary, from 2-3 days to 1-2 weeks. The rash that appears after a fever is commonly caused by viral and bacterial infections, and viral infections include chickenpox, early childhood emergency rash, and measles. Patients with chickenpox usually develop a rash 1-2 days after a low-grade fever, which appears as a central blister with a peripheral redness, usually on the face and neck, forehead and back, extremities and scalp, and usually takes 2 weeks to crust and dry, with the scabs falling off, leaving a reddish-brown pigmented spot or light scar that takes months or years to resolve. If the rash is an early childhood emergency, the onset is usually rapid, with the rash starting on the neck and trunk and rapidly spreading to the back of the ears, buttocks and proximal extremities, all appearing within 1 day. The rash subsides 1-2 days after the fever subsides, and there is no significant pigmentation after the rash subsides. In contrast, patients with measles usually develop a red rash about 3-4 days after the onset of fever, starting behind the ears and gradually progressing to the whole body, which usually subsides in 3 days but may be accompanied by skin flaking that lasts about a week. For rashes caused by bacterial infections, most commonly scarlet fever, patients will generally develop a red rash all over the body after 1-2 days of fever, and the skin will begin to molt and improve after 3-5 days. It is also important to identify the drug rash caused by the use of medication after fever. For the above reasons, the rash after fever is usually transient and can subside on its own in 2-3 days, with the longest period not exceeding 2 weeks. Patients are advised to drink more water, take more rest and eat lightly when the rash appears, and not to panic.