Rhiannon Ingle
Periods, periods, periods.
No matter how many years many of us have had them now, it seems we're still given whiplash when they inevitably show up each month (or whatever your particular cycle pattern is) and bring along with them a whole bunch of symptoms.
Whether it's mood swings, painful cramps, skin breakouts, bloating, food cravings, fatigue, problems sleeping, body dysmorphia, a non-existent sex drive or any of the other countless side-effects of bleeding - it's a given fact that periods can really suck sometimes.
But, interestingly, a lot of people who have periods comment on the second day of them being the worst of all.
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And this is far from an old wives' tale as health experts have actually now finally confirmed exactly why day No. 2 can be so brutal.
Like many things, it's actually all down to hormones.
Well, specifically, prostaglandins which appear when your progesterone levels lower.
They also peak on the second day of your period - hence why the pain seems to peak around that point also.
Speaking to Metro, Dr Fatema Mustansir Dawoodbhoy, academic doctor specialising in obstetrics and gynaecology, who works with the upcoming period care app Joii explained: "As the lining of your uterus breaks down, prostaglandins (hormone-like chemicals) are released in the body."
According to the expert, excess prostaglandins are thought to be the key reason for those horrific cramps you feel on the second day of period as they encourage the uterus to contract, 'helping to shed the old endometrial tissue released from your body as period blood'.
She added: "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 take place during the first few days of the menstrual cycle can also impact our perception of pain because, as well as progesterone, oestrogen levels also drop at the beginning of your 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 doctor and researcher who also works with Joii, also noted.
Additionally, blood flow is typically heavier on the second day of your cycle.
Dr Ashfaq Khan, a consultant obstetrician and gynaecologist and founder of Harley Street Gynaecology, says that this can contribute to more painful cramps.
"The second day of the period is typically associated with a heavier menstrual flow for many women," he told the outlet. "The increased blood volume can lead to more intense cramping and discomfort as the uterus works harder to expel the menstrual blood."
Well, the more you know - eh?