Rulings on istihaadah

In the answer to question no.
68818
we explained when bleeding is menses (hayd) and when it is isthaadah. When
it is menses then it is subject to the rulings on menses, and when it is
istihaadah it is subject to the rulings on istihaadah. 

The main rulings on menses have been mentioned in the answer
to question no 70438. 

The rulings on istihaadah are like the rulings on purity
(i.e., when one is not menstruating). There is no difference between a woman
who is experiencing istihaadah and a woman who is not menstruating or
bleeding, except the following: 

1 – She has to do wudoo’ for each prayer, because the Prophet
(peace and blessings of Allaah be upon him) said to Faatimah bint Abi
Hubaysh: “Then do wudoo’ for every prayer.” Narrated by al-Bukhaari in the
chapter on washing away blood. What that means is that she should not do
wudoo’ for a prayer that is to be performed at a particular time until the
time for it has begun.  If it is a prayer for which there is no particular
time, she may do wudoo’ for it when she wants to perform the prayer. 

2 – When she wants to do wudoo’, she has to wash away the
traces of blood, and put a piece of cotton over her private part to hold
back the blood, because the Prophet (peace and blessings of Allaah be
upon him) said to Hamnah: “I suggest you use a piece of cotton, for it will
absorb the blood.” She said: It is more than that. He said: “Use a cloth.”
She said: It is more than that. He said: “Then tie it tightly around
yourself.” Then whatever comes out after that will not matter, because the
Prophet (peace and blessings of Allaah be upon him) said to Faatimah
bint Abi Hubaysh: “Do not pray during the days of your menses, then wash
yourself and do wudoo’ for every prayer, then pray, even if the blood falls
onto the mat.” Narrated by Ahmad and Ibn Maajah. 

3 – Intercourse. The scholars differed as to whether it is
permissible when one is not concerned about suffering hardship as a result
of giving it up. But the correct view is that it is permissible in all
cases, because many women, ten or more, experienced istihaadah at the time
of the Prophet (peace and blessings of Allaah be upon him), and neither
Allaah nor His Messenger forbade them to have intercourse. Rather the words
of Allaah – “keep away from women during menses” [al-Baqarah 2:222] –
indicate that it is not essential to keep away from them at other times.
Also, it is permissible for her to pray, and intercourse is a less serious
matter. Drawing an analogy between intercourse with a woman experiencing
istihaadah and a woman who is menstruating is not correct, because they are
not the same, even in the view of those who think that it is haraam, and
analogies are not valid if the two things concerned are different. End
quote. 

Risaalah fi’l-Dima’ al-Tabee’iyyah li’l-Nisa’
by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him).