A woman who is niddah should dress modestly in her husband's presence, since he is not permitted to look at the parts of her body that are generally covered. But he may gaze at her face, or other areas that are normally exposed, even if this gives him pleasure.
At the time of the Beit HaMikdash, when the laws of ritual purity were practiced, women wore special clothes while they were niddah to alert others of their status. Although this is no longer required, some couples continue the practice as a subtle reminder (e.g. she wears a certain item of jewelry). The wife should not go out of her way to be enticing. She should, however, continue to dress nicely, in order not become unattractive to her husband.
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