Small bumps on the face when it is hot may be a manifestation of rosacea, and may also be heat contact urticaria, which needs to be analyzed specifically. 1. Rosacea: Rosacea is a chronic inflammatory skin disease characterized by persistent erythema with dilated capillaries. It is characterized by the symmetrical occurrence of erythema in the middle of the face, especially in the nose, cheeks, forehead and jaw, etc. When the external temperature suddenly rises or the temperature difference suddenly changes, pinpoint to mung-bean sized rashes and pustules will appear on top of the erythema. 2. Thermal contact urticaria: the cause of this disease is divided into congenital and acquired, acquired thermal contact urticaria and constitution, patients usually try to avoid heat stimulation, exercise to improve their physical fitness, the use of moisturizing cream to repair the skin barrier. There may be other reasons for the small bumps on the face when it is hot, so it is recommended to go to the hospital in time to clarify the cause of the disease and treat the symptoms.