Hi there,
Defo no risk here, protected (Condom) sex carries no risk of HIV Infection, - you really are fine to move on and forget about this.
In answer to your question, your allergies would make no difference at all to your chances of catching HIV.
In terms of her rash, it could be eczema / dermatitis / psoriasis, - does not mean she had HIV.
Our minds can play tricks on us but you really are fine from the above situation - Kudos for using Condoms - always do this to keep safe :)
You had protected vaginal sex. Unless the condom broke, there should be no risk. But in the future I would use this as a lesson learned. All the best.