This idea may have a limited audience...but since the OP asked: In addition to the stash of toiletries a hotel might have on hand, either in rooms or behind the desk, another suggestion would be to have some unscented/hypoallergenic options, even if on a limited basis. As someone who has learned the hard way that I'm becoming increasingly sensitive to some scented items like soap, lotion and laundry detergent, I try to have what I need in my 3-1-1 baggie. But on the back end of a longer trip things may start to run out, and, as said, there's not always an open store close by to resupply.

My luggage went missing on an AirFrance connection CDG-OTP a few years ago so the local station gave us an amenity kit similar to what you'd get in Business/First class...with some notable additions including a t-shirt, cologne & a condom. It took 2 days for all of our group's luggage to arrive. One of the bigger guys in the group had an interesting experience trying to buy new clothes in the street market of a small Romanian village.