Itchy red bumps on the face when it is hot, consider and skin sensitivity, atopic dermatitis, cholinergic urticaria and other factors related. 1. Skin sensitivity: the skin cuticle is thin, the skin is more sensitive, by the hot and cold stimulation, may lead to redness, goosebumps on the face. It is recommended to take good care of the skin, usually avoid the stimulation of hot and cold alternation, and give medical skin care products under the guidance of the doctor to regulate. 2. Allergic dermatitis: patients with allergies are exposed to allergens, which enter the body through inhalation, contact, injection, food and other channels, and the body undergoes an immune response, resulting in redness, itching and bumps on the skin. 3. Cholinergic urticaria: Cholinergic urticaria is also a type of urticaria, where the patient is stimulated by heat, resulting in a slight increase in body temperature. If the thermoregulatory center of the brain is stimulated, the cholinergic plexus is excited to release acetylcholine, resulting in redness and bumps on the skin. Sometimes redness and bumps on the face, it is recommended to avoid undesirable stimuli. Follow the doctor’s instructions for treatment.