Whenever it is hot indoor and outdoor my skin (whole body)starts to itch all of a sudden though short lasting.sometimes turns red.what is it &any cure?

Mild "allergy.": This does NOT sound like a true allergy. However, some people can develop a skin sensitivity to any number of things. Occasionally, they can be extra sensitive to their own sweat. You can try an antihistamine such as loratadine or cetirizine once a day to see if it helps. Also consider a food journal to see if your diet has influence on these symptoms.