Dreaming of allergy means sensitivity to surroundings that keep you unfocused and unable to complete your tasks. Reaching your full potential is not possible as something is always irritating you.
Reevaluate your work surrounding, and throw out things that cause distractions. Separate work from play, and you will once again operate at optimal levels.
In dreams, an allergy represents something that you are uncomfortable with or something you want to avoid. For example, if someone had an allergic reaction after eating chocolate, then they may feel uncomfortable with chocolate or want to avoid it in their diet because they think it will cause another reaction like before.