Why You Get Gas And Diarrhoea When You Have Your Period

Today we’re addressing a question from folks with uteruses who find themselves spending way too much time in the bathroom once a month.

Illustration by Chelsea Beck/GMG

A Lifehacker reader wrote to us with this question:

OK, I’ve always wondered why I get terrible gas the first day or two of my period. Seriously. What does the reproductive system have to do with my colon?

This is a highly requested question, I’ll have you know, because when I told my Facebook friends I was looking for weird health questions, one replied immediately: “Let’s talk period diarrhoea, ladies.” If you take nothing else away today, make it this: Period diarrhoea, and period nuclear farts, are definitely a thing. It isn’t just you.

And Dr Ellen Stein, a gastroenterologist at Johns Hopkins, knows why. “I can give you a one-word answer: Prostaglandins.”

“Tell me more,” I said.

She explained that prostaglandins help the cervix to open during menstruation and the uterus to expel its contents. Prostaglandins are hormone-like chemicals that our body naturally produces, and even when they’re aimed at the reproductive tract, they can also end up affecting the gut.

So as your uterus is squeezing out its contents, your intestines may get the idea to do something similar. On the flip side, there’s a shortage of these prostaglandins when you’re pregnant (gotta hold that baby in), which can lead to constipation.

Some people are more sensitive than others to the effects of the prostaglandins. If that’s you, you’ll get crampy diarrhoea and, yes, gas at that time of the month.

So what can you do when prostaglandins strike? Ibuprofen is a good option, Dr Stein says, not just because it relieves pain, but because its anti-inflammatory actions also help to ramp down the prostaglandins a little bit. A hot water bottle also tends to relax the gut, plus it feels good.

But remember, your menstrual cycle is a month-long thing. Hormones fluctuate the whole time. So chances are, if you have diarrhoea at that time of the month, you may well be constipated at some other time of the month. A period and symptom tracker, or a simple grid in your journal, can help you figure out if there’s a pattern.

Once you get a handle on your intestines’ monthly schedule, start paying attention to “farty foods” that give you more gas. You’ll want to avoid those on the day or two before your period. But earlier in the month, when you’re more likely to be constipated, feel free to eat more of your favourite fibre-containing foods, and wash them down with plenty of water. Probiotics can help too (Dr Stein mentioned Activia). And if you fear that won’t be enough to keep things moving, an over-the-counter stool softener might help.