According to the Arab Muslim Religion they say that Menstrual Blood is unclean. This vision stems even from the Jewish Religion where women were not supposed to be even touched when they are in their menstrual cycle..
For me as a woman I found this to be denigrating and unjust against the female biology and sexuality. The case is actually that menstrual blood is a holy blood in the sense that it is part of feeding a possible baby (the Uterine of the Womb of the Woman that lets go every month). The problem of this difference of opinion is that women are looked down upon when they have their period and that women should be "shameful" or "hiding" their period even during their teenager years. This is really not the right way to raise a female perspective of healthy bodily image and female biology.
The reality is that you can touch a woman, hug a woman, kiss a woman and even have sexual intercourse during her period if she pleases. This is not something that all women and men understand, but sexual or physical intimacy during a period can actually relieve the pain, the headaches and the cramps. It seems unusual but it's still part of the female biology and psychology. This is obviously not for everyone, but it can be worth a try in a steady relationship if you both are up for this. This kind of bleeding is or can be actually arousing and is not especially a turn off.
Physically and emotionally the woman however does need time off, but sexual intimacy is part of relaxation if it is good, healthy and relaxing sexuality.