Why you bruise more easily when you drink alcohol

A glass of beer is served at a bar in Madrid, March 3, 2016. REUTERS/Juan Medina - RTS9ALD

A dry mouth, a pounding head, and an upset stomach: Those are just a few side effects you might expect after drinking alcohol the night before.

One you might not think of? Waking up with black and blue marks across your body.

That’s because boozing can make you more susceptible to bruising.

Alcohol is a vasodilator, meaning it causes your blood vessels to temporarily relax and expand.

This widening increases blood flow throughout your body, including near the surface of your skin, said Scott Swartzwelder, Ph.D., coauthor of “Buzzed: The Straight Facts About the Most Used and Abused Drugs from Alcohol to Ecstasy.”

More blood flowing through your vessels means that more blood can escape if a blood vessel happens to get ruptured—say, if your leg bumps the corner of a table, Swartzwelder said.

And when the blood vessels underneath your skin break, it causes blood to leak out. That’s the purplish-blue color you see with a bruise.

So when you drink alcohol and injure yourself, you can be left with a bigger, more noticeable bruise than you might see while sober.

It doesn’t take a lot of alcohol for the effect to occur, either: Men may notice an increased risk of bruising after just a couple of drinks, Swartzwelder said.

Plus, you’re more susceptible to an accidental fall or bump after you’ve been drinking, anyway.

Alcohol impairs your cerebellum, the part of your brain that’s responsible for coordinating your movements, Swartzwelder said. So after a few drinks, you start to become more clumsy.

And your injury might not even hurt at the time.

Booze has an analgesic effect, meaning that it dulls pain.

“So you might bump into the table and just brush it off,” Swartzwelder said.

Alcohol also impairs your memory, so you might forget about your accident altogether—until you wake up the next morning wondering where that giant, painful bruise came from.

For the average healthy guy (say, drinking one or two drinks per night, or fewer than 14 drinks per week) the alcohol-related effects on bruising are temporary, and no real cause for concern. They should dissipate after three or four days.

If your bruise doesn’t improve within two weeks, or if you start to notice frequent, unexplained bruises—whether you’re drunk or sober—call your doctor.

Bruises that take a long time to heal or getting bruised for no apparent cause could be signs of a bleeding disorder.

This article originally appeared on MensHealth.com.