My skin is easily allergic. Once the weather is hot, or after exercise, my forearm, calf and neck will appear erythema. What should I do?

According to the symptoms you described, it may be cholinergic urticaria.

More common in young people, due to exercise, heat, emotional tension, eating hot drinks, etc., the deep body temperature rises, prompting acetylcholine to act on mast cells.

It is recommended to go to the hospital for treatment. You can do allergen testing, find out the causes, treat the symptoms, and avoid contact with substances that can cause allergies in your life.

I wish you a speedy recovery!