Lots of people feel low or irritable in the days before their period. This is part of premenstrual syndrome (PMS) and it's very common. For a smaller number of people, these feelings are severe enough to get in the way of daily life. This is called premenstrual dysphoric disorder, or PMDD.

Acne is one of the most common skin problems in teenagers and young adults and many also notice their skin gets worse in the days before their period. Both have the same root cause, which is the way hormones affect the oil in your skin.