Feeling terrible

So I feed my daughter clothed most of the time and roll her sleeves up. The past few days she's been getting hives and I'm having to go backwards now and feed her one single thing just to see what it is. I just feel awful because what if it's been going on for awhile now but I just didn't see. 😪 when I changed her diapers before I never saw anything. Maybe it's just starting to pop up? I don't know bur I feel terrible.