A new study reveals that heavy drinking can worsen the effects of illness and weaken your immune system against viruses.

To see how alcohol affects resistance to infection, Gyongyi Szabo of the University of Massachusetts Medical School in Worcester and colleagues exposed infection-fighting white blood cells to chemicals that mimic viruses and bacteria. "Half of the cells were also soused in the levels of alcohol that a person might have in their blood after quaffing four or five alcoholic drinks daily for a week," wrote British scientific magazine New Scientist on the study.