Our immune system plays a major role in helping the body fight disease-causing agents, which enter our body from the environment. If the immune system is strong enough, a number of dangerous and possibly life-threatening diseases can be prevented. There are also a few ways which are harming your immune system unknowingly; have a look at them, here. Drinking Excess Alcohol - Drinking more than a glass of alcohol on a daily basis or getting "drunk" regularly can be a blow to your immune system as the toxins in alcohol can weaken your immune system to a great extent. Travelling Too Much - Being exposed to new environments, climate, water and food often and the lack of rest, can all come together affect your immune system. Being Overweight - Besides high cholesterol, high BP, heart problems, etc researches say that, the hormonal imbalances created in the body, due to excess fat accumulation can harm the immune system.