Fostering a dog we would like to adopt- but get welts when I am licked,?

We are fostering a dog for the week that we have come to love. We need to give the humane society an answer by tomorrow. I have discovered that I get hives and sometimes welts on my arms and face when she licks me. I also am a tad congested. I have been taking claritin daily so this is while I am on allergy meds. Will the allergy go away or lessen or will it get worse? I don't want to make a 20 year commitment to this dog and be miserable for all of it. Also, she has extreme aggression to our other little dog when they eat together- will this ever go away? I don't want my other dog to live in fear. Other than that, she is the perfect dog for us. What should I do?