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Perspiration is easy to get from the water with chlorine. Deodorant, perfume, body lotion, hair spray and the like can be more difficult. If you use a lot of these products you should shower first. If you don't use a lot of these products you may never have a problem even if you don't shower off.
i always take a shower after soaking. i know the instructions say i should before, but if hot tubbing starts becoming a chore i'm less likely to do it.