When you sweat, your body is getting rid of toxins in your body. That means what you ate also. Like people who eat alot of garlic will start to smell like garlic when they sweat, with you, you itch. I don't think you are allergic to anything. It may just be what you ate or you might be sensitive to the sweat. It is full of potassium and salt. This can make you itch till you bathe.