First let me start by assuming you mean itching down there rather than itching all over your body. In the days before your period a lot is happening. The hormone progesterone really decreases since you aren't pregnant and the hormone estrogen slowly starts to rise again to get your ovaries ready for the next cycle of ovulation. Your body wants to maximize the chance of pregnancy (which is why birth control is SO important all the time) and so those wacky hormones are cycling, trying hard to make that happen. In the couple of days before your period, it's clear to your body that pregnancy isn't happening and the shift in hormones begins and sometimes the progesterone decreases a lot but the estrogen doesn't quite get up to speed. When this happens, your vagina can get somewhat dry and this is itchy! Once your period starts, the menstrual flow moistens things again and by the time your period is done the estrogen is kicking in and making you moist again so the itching is gone. Of course if you're itching all the time or having some cheesy white or foul smelling discharge you should see your healthcare provider because itching that lasts for a more than a couple days or is associated with yucky discharge could be something that needs treatment.
A lot of women experience this problem and I’m sure that Dr. Molly will explain the medical reasons why this happens, so be sure to check out her answer. I’m here to let you know that you are not alone. Sometimes an itchy feeling can occur from changes happening to your body physically and adjusting your routine (body washes, sprays, etc) and/or clothing (sticking with cotton underwear, etc) can help. For some women, simply drinking more water can lessen the itchy feeling. If nothing alleviates the feeling and it is disrupting your life, definitely see your healthcare provider.
Girl, you stumped me! I've never experienced that before but, of course, everyone has different periods. I know health expert Dr. Molly will be able to shed some light on your itchy dilemma. Check out what she has to say.