From The MS Information Sourcebook, produced by the National MS Society.
Alcohol is a powerful drug. If abused, it produces multiple effects on the central nervous system and other organs of the body. Acute alcohol intoxication can cause loss of balance, uncoordinated movements, slurred speech, and impaired judgment and thinking. Chronic alcohol abuse commonly results in numbness, tingling and loss of sensation, tremor, lack of coordination, dementia, and may damage the liver, stomach, and other organs.
Some people with MS report that some of their neurologic symptoms, especially imbalance and lack of coordination, temporarily worsen after even one drink. Since alcohol depresses the central nervous system, it may also have an additive effect with certain medications that are commonly prescribed for MS. These include baclofen, diazepam, clonazepam, and some antidepressants. For all of these reasons, people with MS should talk to their physician about how much alcohol is appropriate for them to drink and how often.