Girls experience severe period cramps occur because of an excessive amount of prostaglandins present in the body. Prostaglandins are compounds which are released during the shedding of the uterine lining. Period cramps are usually experienced in the abdomen, thighs and the back. Prostaglandins support the uterus to contract and relax to let endometrium detach and flow out of the body. Excessive pain is caused when the uterus contracts strongly, blood flow is less and the supply of oxygen to the muscle tissue is decreased.

Advantage of using a hot water bottle or a heating pad is that it provides comfort and aids in killing the pain at a molecular level. When heat is applied to the skin, the heat receptors get switched on and block the effect of chemical messengers causing the pain. A hot water bottle is known to help in relaxing the uterus, reducing the tightening of blood vessels and improving the blood flow to the uterus.  One should use a heating pad/hot water bottle wrapped in a towel for safety purposes.

Heat is known to open up the blood vessels and promote blood flow. The blood flow increases with the help of heat which helps in relaxing the tight muscles and washing out the buildup of lactic acid which leads to soreness.