It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said that a woman came to the Messenger of Allah (peace and blessings be upon him) and said: I suffer from istihadah (irregular bleeding). He (peace and blessings be upon him) said: "That is not menstruation; it is only the blood of a vein. Let the woman refrain (from prayer) during the days of her usual cycle, then perform the ritual bath (ghusl), then bind herself with a cloth and pray."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19863