The thing with a sensitive skin means there is a greater possibility of it reacting! My daughter gets really bad eczema and the one thing that really sets it off is hard water ... yup water!!! So the best thing with a sensitive skin is to do a patch test with any products to make sure. But then again with my daughter one minute she is fine with stuff and then when she has a flare up she has to avoid them til her skin settles down. The products she use don't necessarily set it off, but they can aggravate it during a flare up. I have had clients who have mega sensitive skins and are absolutely fine with Nimue, more so than most traditional brands which tend to have a high perfume content for example.
When having a salon AHA treatment clients are best to avoid the sun for a few days due to the deep exfolitation. When having a medical AHA treatment with a full on Glycolic peel then I beleive this is extended to weeks. And of course clients should wear an effective sun screen all the time anyway,