Regardless of how long we’ve had them, it appears that we’re still prone to whiplash when they appear each month (or whatever your unique cycle pattern is) and bring a variety of symptoms. Periods can be incredibly unpleasant at times, whether due to mood swings, agonizing cramps, skin breakouts, bloating, food cravings, lethargy, problems sleeping, body dysmorphia, a lack of sex desire, or any of the other numerous bleeding-related side effects.

Interestingly, many people who have periods say that the second day is the hardest. And this is not a myth; health professionals have now confirmed why day two can be so painful. Like many other things, it’s all about hormones. Prostaglandins are produced when progesterone levels fall. They also peak on the second day of your cycle, which explains why the discomfort seems to peak at the same time.

Dr. Fatema Mustansir Dawoodbhoy, an academic doctor specialized in obstetrics and gynaecology who works with the new period care app Joii, told Metro that “as the lining of your uterus breaks down, prostaglandins (hormone-like chemicals) are released in the body.” According to the expert, additional prostaglandins are thought to be the primary cause of the painful cramps you get on the second day of your period.

Because they induce the uterus to contract, ‘helping to shed the old endometrial tissue discharged from your body as period blood’. She went one step further: “The prostaglandins also constrict the blood vessels in the uterus, reducing the amount of oxygen the uterine tissue receives, and this leads to cramping and pain.” Other hormonal changes that occur during the first few days of the menstrual cycle can also influence our pain perception since, in addition to progesterone, oestrogen levels decrease at the start of the cycle.

“This means that other painful conditions like migraines or fibromyalgia can worsen when you have your period, as the hormone oestrogen falls to its lowest level,” Dr Emilie Côté MRCOG, an obstetrics and gynaecology physician and researcher who also works with Joii, noted.

“The second day of the period is typically associated with a heavier menstrual flow for many women,” the reporter told the newspaper. “The increased blood volume can lead to more intense cramping and discomfort as the uterus works harder to expel the menstrual blood.”