What Causes Nausea Upon Intake Of Milk Products?

I have a 15 year old daughter who, over the past 8 months or so, appears to have developed at least three new allergies/intolerances. The first was to hot peppers - she became tingly and had trouble breathing. The reaction was relieved by Benadryl. Next started about a month ago, she started breaking out in hives on the back of her neck and face when she was outside. Again, Benadryl alleviated things and we began eliminating any possible change for reaction. Sun/UV is all that makes sense. She is outdoors all the time and never had issues. The next one was just this week, and that s dairy. She had milk on cereal and became nauseous right after. She then told me she felt the same the other day when she ate some cheese. She has been a cheese lover all her life and never had an issue. Overall, in addition to that, she generally feels bad and has been sick frequently, just colds etc. but sick none-the-less. I am worried there is an underlying cause for the sudden changes in her health. Allergies we can deal with, but what is causing them to develop and flare up now, so suddenly? They are not hereditary.