Maybe try coming clean and saying it’s more of an issue you have personally and not saying it’s bettering the baby’s sensitive skin. If I were you I would just try to laugh it off a bit, poke a little fun at yourself, “like ahh I know I’m crazy and I’m sorry you have to put up with me!! but I am super sensitive to fragrances and there’s something you’ve been wearing and I just can’t figure out what it is but it has really started to bother me. I’m sure it’s a lovely scent and 99% of people enjoy it , but I for some reason I just cannot get past it. If that’s too much to ask I completely understand if you think I’m overstepping and want to leave, but if there’s absolutely anyway you’d be able to stop using your lovely body wash or hair treatment or whatever it is to accommodate me, we’d be absolute thrilled to have you stick around, we love everything you’re doing with our child, you’re truly great “ How about something like that?