Ask the Doctor: Justin McWilliams

Q: How does alcohol affect the blood, and what can the results be for an HHT patient?

Dr. Justin McWilliams, Co-Director of UCLA HHT Center: Alcohol has several effects on the blood which are relevant to HHT patients. First, alcohol acts to inhibit platelet aggregation, meaning the platelets that make your blood clot become less sticky, making your blood thinner. This explains why moderate alcohol consumption (1-2 drinks per day) is thought to be good for heart health, since it may help prevent formation of clots in the heart vessels, which causes a heart attack. However, in an HHT patient, thinning of the blood may cause worsening of nosebleeds or GI bleeding.

Alcohol consumption also causes vasodilation, meaning blood vessels can enlarge slightly- this in part can account for the warmth and flushing felt with alcohol. Again, this can be a favorable for narrowed or blocked vessels, in the heart for example, but dilation of the telangiectasias (and the arteries which supply them) in HHT patients could increase bleeding.

Anecdotally, alcohol (particularly red wine) has been one of the most common triggers of nosebleeds in my HHT patients. That being said, a large portion of HHT patients tolerate alcohol without ill effects, which underscores the complexity of the disease and of the blood clotting pathways, which cannot always be predicted in an individual patient. I counsel my HHT patients to enjoy alcohol as they wish, but to pay attention to whether alcohol triggers bleeding - if so, limiting or eliminating alcohol is a reasonable strategy to reduce bleeding.