What causes period flu?

It’s complicated, and can vary from person to person, but it seems that – predictably – our hormones are to blame.

“Period flu is in fact likely to just be part of what we would consider premenstrual syndrome,” says Dr Zoe Watson, GP and founder of wellbeing platform Wellgood Wellbeing. “It is down to what is happening with our sex hormones and related body chemicals during our menstruation.”

In this case, the main culprit is a group of chemical compounds called prostaglandins.

“Prostaglandins are produced by the body in many situations, and one of these is in the latter half of our menstrual cycle,” explains Dr Watson. “After we have ovulated, the levels of oestrogen in our body start to drop and our progesterone levels rise. Then, immediately before menstruation, there is a sharp dip in both progesterone and oestrogen.

“This lower level of progesterone causes a chain reaction which ultimately results in the release of prostaglandins by the uterine or womb tissue.”

Dr Watson adds that in this scenario, the main function of prostaglandins is “to cause the womb to contract to aid the shedding of the womb lining during our period – but they are also released in other situations when we encounter infection and inflammation.”

Because we produce the same chemicals when we actually are ill, we can feel the same way when these compounds are released pre-menstruation. It’s also thought that this inflammatory response can cause our immune system to go into overdrive, making us feel distinctly under the weather.

Period flu: why you might feel ill around your time of the month