All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If a woman has blood discharges which do not stop after fifteen days or continue for a period of more than fifteen days, then it is bleedings outside her normal menses, and such a woman should rely on her normal menses if she has any. Therefore, she should refrain from praying and fasting and after this period, she should perform Ghusl (i.e. ritual bath) and then perform the prayer. However, if her menses continue and she does not have a fixed period of menstruation, but she may distinguish between the types of blood -as the blood of menses is black and thick and has a smell, and causes some pain to the woman-, in such a case she should rely on her distinction of the types of blood. Nonetheless, if she has no monthly periods or she cannot distinguish between the types of blood, in this case she should do like other women in her case, like her sister or her mother, and then she should purify herself after that period and perform the prayer and fast.
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Allaah Knows best.