With cold and flu season quickly approaching, the next time you're sick, you might want to praise your fever for aiding in the battle against infection. This is because scientists have discovered additional evidence that increased body temperature improves the function of particular types of immune cells. Moreover, there are several ways to raise your body temperature gently without using any energy-consuming methods such as heating pads or medicines. The first way is by exercising more. Physical activity increases blood flow to the skin, which in turn raises body temperature. You can estimate how much exercise you need by multiplying your weight in pounds by 0.67. For example, if you weigh 180 pounds, you should do around 20 minutes of strenuous activity daily to keep yourself warm. However, only doing enough exercise to keep yourself healthy not to injure yourself. Too much exercise is also bad because it can lead to heat injury. Another way to raise your body temperature is by drinking plenty of water and non-caffeinated beverages such as tea and coffee. The more water you drink, the more fluid you produce through your urine and feces, which removes excess heat from your body. Similarly, caffeine stimulates your nervous system which makes you sweat even when it's cold outside, so it helps keep you warm too. However, it's important to avoid overdoing it: too much caffeine can cause anxiety and irritability.