There are many reasons why your back itches when it gets hot, such as contact dermatitis, eczema, hives, etc. 1. Contact dermatitis: Contact dermatitis may be related to exposure to various exogenous allergens and may manifest as rashes and itching. It may be caused by an increase in perspiration when the back is hot, thus causing itching when the back is hot. 2. Eczema: the cause of eczema is more complex, the onset of eczema can cause the phenomenon of itching when the back is hot, and may also be accompanied by localized red rashes, papules, blisters and other phenomena. 3. Urticaria: skin contact with external allergens, especially food allergies, can show the phenomenon of itching on the back when hot, especially cholinergic urticaria, symptoms will appear after the skin is hot. There are many reasons why the back itches when it is hot, and it is recommended that the patient go to the hospital in time to improve the examination and take standardized treatment according to the doctor’s instructions, and not to ignore the symptoms and take it lightly.