I have very sensitive skin and tons of allergies, esp to anything with perfume in it.

I have used Chamois Buttr for nearly every ride. I put it "all over" esp at the creases. It is magic stuff. Never a problem. If I am only doing a 10 mile ride I won't bother, but it is worth twice the price as far as I'm concerned. If I forget to bring it I will start feeling irritation after about an hour. So not only do I really make an effort to remember to apply it before a ride, I also keep a couple of sandwich baggies with a squirt of chamois butter in the corner, all rolled up in my handlebar bag should I need to reapply on a long ride, or if I wipe too much away on a pit stop. The baggie method is great - just turn it inside out and the baggie becomes your applicator, so you have clean hands afterward. When done, just turn it back inside out and throw away, or put in your pocket to throw when you get to a trash can. Typically I'll make up a bunch of these at a time, so I always have some handy. Much cheaper than buying the "individual servings." And very handy if you are commuting to work.