From Sahih Muslim (Hadith 3742):
Umm 'Atiyya ('Allah be pleased with her) said:We were forbidden to observe mourning for the dead beyond three days except in the case of husband (where it is permissible) for four months and ten days, and (that during this period) we should neither use collyrium nor touch perfume, nor wear dyed clothes, but concession was given to a woman when one of us was purified of our courses to make use of a little incense or scent
Reference: Muslim 3742