What is istihadah (irregular non-menstrual bleeding) and how is ritual purity achieved from it?

The questioner : Honorable Shaykh, among the letters we received by fax, this questioner says: What is istihadah (irregular non-menstrual bleeding), and how is ritual purity achieved from it?

The Shaykh : Istihadah (irregular non-menstrual bleeding) is when blood continues on a woman for all or most of the time. She has two, rather three, conditions. The first condition is that the woman is accustomed to menstruation, meaning she has a regular menstrual cycle before she is afflicted with this illness. In this case, she reverts to her custom, meaning she sits out the time of her custom and the number of days of her custom, then she performs ghusl (the full ritual bath) and prays. For example, a woman whose custom is that menstruation comes to her on the first day of the month and lasts with her for six days, and then she developed istihadah (irregular non-menstrual bleeding) afterwards. We say: she sits out the first six days of every month, then she performs ghusl (the full ritual bath) and prays. Generally, if a woman with istihadah (irregular non-menstrual bleeding) wants to pray, she washes her private parts, protects herself with a pad, performs wudu' (the ablution for prayer), and prays as much as she wishes, whether obligatory or voluntary prayers. She may read the Qur'an. It is permissible for her husband to have intercourse with her, except that it is better that he does not do so unless he fears hardship from abstaining from intercourse.
The second condition is that the woman has no custom, meaning istihadah (irregular non-menstrual bleeding) has come to her since the first time menstruation came to her. In this case, she reverts to distinguishing. That is, she looks at the blood. Yes. If some of it is different and indicates that it is menstruation, and some is not, then she sits out the blood that indicates menstruation, then she performs ghusl (the full ritual bath) and prays as mentioned before. The scholars said that distinguishing is done by color, smell, and thickness. The color of natural menstruation is black, its smell is foul, and it is thick, not thin. This is what the jurists (may Allah have mercy on them) said. Blood with these characteristics is menstruation, and thin blood that has no smell and the color of ordinary blood is istihadah (irregular non-menstrual bleeding). The third condition is that the woman has no custom and no distinguishing feature in the blood. In this case, she sits out from the beginning of the period in which menstruation first came to her, for six or seven days, then she performs ghusl (the full ritual bath) and prays. For example, a woman who developed istihadah (irregular non-menstrual bleeding) from the first time menstruation came to her, so she has no custom and her blood is uniform without distinction. We say: sit out six or seven days from the beginning of the period in which menstruation first came to you, then perform ghusl (the full ritual bath) and pray. If the beginning of the period in which menstruation first came to her was in the middle of the month, that is, on the fifteenth day, we say: whenever the fifteenth day comes, sit out six or seven days, then perform ghusl (the full ritual bath) and pray. It is good for a woman afflicted with continuous bleeding to present herself to a specialist doctor in this matter, perhaps she will find a cure for her. May Allah reward you.