Red bumps on the face in hot weather may be caused by rosacea, cholinergic urticaria, or polymorphic sun rash, and it is recommended that the patient be treated with medication under the guidance of a doctor to clarify the specific cause of the disease. 1. Rosacea: Rosacea is also clinically known as rosacea, which is characterized by persistent dilation of facial capillaries, exacerbated by heat, and can appear on the basis of erythema as a pinpoint to mung bean-sized rash, pustules. 2. Cholinergic urticaria: mostly seen in young patients, heat prompts cholinergic nerve impulses and release of acetylcholine, which acts on mast cells and develops. Manifestation for a few minutes after the stimulation of the appearance of round papules, surrounded by a varying degree of redness. Self-conscious itching, tingling or burning sensation, can be subsided in 30-60 minutes. 3. Polymorphic sun rash: generally aggravated in spring and summer. Reduced in fall and winter. Mostly seen in young and middle-aged females, occurring in exposed areas (such as the face, back of the neck, neck before the V-shaped area, the back of the hand and the forearm extension). Often in the sun within 1 hour of self-conscious itching, a few days after the appearance of skin lesions. The lesions are of various forms, commonly papules, papules, but also can be manifested as edematous erythema or plaques. Red bumps on the face in the heat of the day may also have other causes, it is recommended to go to the regular hospital for examination in a timely manner, under the guidance of a professional doctor for standardized treatment.