1,098. Chatzitzos

160:6 In a place where the practice is for women to immerse after Shabbos or yom tov, a Torah authority must be consulted regarding when to perform the chafifah.

161:1 The woman must immerse her entire body - including all her hair - at one time. Therefore, she must check very carefully that there isn't anything interposing between her and the water while immersing. Even something tiny could be considered an interposition (chatzitzah) and invalidate the immersion. It goes without saying that nothing may be on the outside of her body because the water needs to reach there. If something forms an interposition, the water will not touch that area. Even the woman's genitals, where the water doesn't enter, must be free of any interposition so that it would be possible for the water to go there. To speak illustratively, even though the water does not go into the woman's mouth, if there was an interposition between her teeth, the immersion would not be valid. The same principle applies here as well. All places on her body must be clean and possible for the water to reach when she immerses.