Excessive alcohol can damage the immune system because the alcohol will prevent nutrients from feeding your immune system. The alcohol is absorbed into your bloodstream through your stomach. Once in the bloodstream, alcohol will reduce the white blood cell count in the body. The lower the number of white blood cells, the more difficult it is to fight off disease. Alcohol also combines with red blood cells for the process of "blood sludging." In this process, red blood cells clump together and cause smaller blood vessels to plug up. This reduces the flow of oxygen to many vital organs. With less than an optimal amount of oxygen, your organs and your immune system will not operate at peak efficiency.
Amount of Alcohol
Taking one or two drinks a night is not likely to harm your immune system. Three or more drinks a night is a significantly different story. If an individual drinks enough alcohol to get impaired or drunk, it is also enough to cause weaknesses in the immune system. When you drink enough to get drunk, you are also producing an nutrition deficiency. This will weaken your immune system. Additionally, the consumption of alcohol impairs the function of B-lymphocytes, which produce antibodies in the blood. These antibodies ward off viruses and other diseases that may attack the body.
Other Health Issues
Stomach issues can develop with excess alcohol and your immune system will not be able to fight them off. Drinking alcohol leads to increases stomach acid because your stomach must work harder to break the alcohol down. This acid can cause ulcers, liver problems (cirrhosis) and kidney disease. Normally, your white blood cells could fight off these conditions, but not when alcohol intake is high.