Its actually what you inject and the bacteria on your body that produce body odour. Smelly sweat comes from sweat glands located mostly in the armpits but also in the crotch, anus, and a little on the scalp. Sweating is the body's air conditioning system. When sweat is released, it coats the skin to remove heat from the body, and salts and urea are left behind (so thats why your partner always tastes salty when you kiss them after having sex). Sweat glands aren't active for those under age 12; thats why adults smell and children do not. Sweat itself is odourless; your palms have more than 2,000 sweat glands but they don't attract bacteria that cause bad smell. Some foods like onions, garlic, curry and even some medications can give your sweat an extra scent. Some physical changes can cause excess sweat, as happens with infections, menopause, anxiety, and overactive thyroid.