When the day is hot, the skin itchy consider cholinergic urticaria, eczema, prickly heat, summer dermatitis and other factors and cause. 1. cholinergic urticaria: a type of urticaria, generally because the peripheral nerves release acetylcholine and caused by small air skin disease, usually after the onset of heat, which can lead to the local skin appears small and very itchy dotted air. 2. Eczema: the second may also be caused by eczema, some patients have eczema, mainly caused by environmental factors. Generally in hot climates, it can also lead to eczema, which makes the skin itchy when it is hot. 3. Prickly heat: a superficial, inflammatory skin disease common in summer or hot environments. The disease is in the hot and humid environment, sweat pore blockage and rapid occurrence of small pimples and blisters, can appear itchy feeling. 4. Summer dermatitis: a seasonal, inflammatory skin disease caused by high temperatures in the summer, preferably in adult women, can lead to large red patches of skin, which can be accompanied by pimples, pimples, conscious itching. There are many other causes of itchy skin in the heat of the day, and it is best to go to the hospital in time to consult and identify.