The advice I've come across was to avoid washing your little girl's hair when she's in the bath, or to leave it till the last minute, because sitting in the shampoo suds could cause vaginal irritation. I've always completely ignored this advice, though, on the grounds that if I don't wash Rowan's hair the moment she's in the bath, she might have a little accident and the entire bath business has to be abandoned, and then she wouldn't get her hair washed at all, when the whole reason why she's in the bath is usually that she's used porridge as a hair styling product. My reasoning is that baby shampoo is formulated to get into your baby's eyes without harm, so what can it possibly do to her muschi?