Patients who develop a red rash around the mouth may be associated with mosquito bites, contact dermatitis, hand-foot-mouth disease, perioral dermatitis and other factors. 1. Mosquito bites: When the patient is bitten by mosquitoes around the mouth, a red rash around the mouth may occur. 2. Contact dermatitis: when the skin around the patient’s mouth comes into contact with an exogenous substance that triggers contact dermatitis, it may lead to a red rash around the mouth. 3. Hand, foot and mouth disease: Hand, foot and mouth disease is an infectious disease caused by enterovirus infection, patients may appear hands, feet, mouth localized skin rash, pimples and other symptoms. 4. Perioral dermatitis: an inflammatory skin disease mainly characterized by erythema, papules and scales, often occurring on the upper lip, chin, nasolabial folds and nose. It can also appear as a red rash around the mouth. In addition, perioral dermatitis, seborrheic dermatitis, herpes simplex and other diseases may also cause a red rash around the mouth. It is recommended that patients consult a doctor in time for examination and treatment of the cause, pay attention to personal hygiene in life, keep the skin clean and dry, take a light diet, avoid spicy and irritating food.