A study published in the European Journal of Pain found a link between the two, suggesting cognitive pain and "bodily awareness systems" are sensitive to menstrual cycle phases, with experts putting the heightened sensitivity down to a drop in oestrogen levels. According to hair colourists, however, it's not just things like hair removal that maximise the skin's sensitivity, but having your hair dyed, too.
Talking to the Metro, Sophia Hilton, founder of Not Another Salon, advised that bleach specifically is likely to cause more scalp irritation during your period than at other times in your cycle. Hilton says she sees clients twitching in the chair when they are having their hair dyed on their period.
This is something Francesca Dixon, senior creative colourist at Hari's Hairdressers, seconds. She elaborates: "When on your period, your hormone balances not only change and become a little irregular but the body’s reaction to certain chemicals has the potential to change, too. This often makes your skin, especially on your scalp, much more sensitive."
Increased sensitivity isn't the only thing you might face on your period, as Francesca believes that in some cases, it's likely for the colour not to work as well. "Changes in your hormone balance can potentially prevent the dye from taking to hair," she told R29. "This is why we would advise waiting until your period has finished before booking in for any colour treatments."
If you're worried about scalp sensitivity in general, expert colourist, Paco Latorre hits home the importance of a patch test. "This is essential to ensure that you won’t be allergic to the hair dye used. Monitor your scalp for 48 hours after the test, and if no reaction appears it is safe to have your hair coloured." If it is bleach that is being used, Paco suggests avoiding washing your hair 24-48 hours before your treatment, to ensure you don't strip the scalp and hair's natural protective oils. He also advises asking your colourist to supplement hair dye with something like argan oil. Some colourists also use petroleum or coconut oil as a barrier formula to prevent the scalp from being fully exposed to any harsh chemicals that could cause sensitivity.
If it's ammonia your scalp reacts badly to, ask your colourist to talk you through ammonia-free options – yes, they exist. For those who don't have the time or the budget to book in for a professional salon appointment, try Clairol's Nice'n Easy box dye. Instead of PTD and PPD (most commonly the cause of irritation and allergies in hair dye), it enlists a new, breakthrough molecule to minimise the risk of scalp irritation, and is formulated with anti-damage technology, so you can save on extra treatments.