My Aunt P sent out this about an hour ago:
Just a quick note. It is 5 a.m. and we have just returned from the ER. P developed hives tonight. We went to ER and they gave him some Benadryl which has helped. The doctor said not to admit him "yet" until he can talk to the infectious disease doctor. They may try to do something called desensitization assuming this is an allergic reaction to the antibiotic which they are not sure about.
As background, he again has pneumonia caused by the pseudomonas. He has been on 3 different antibiotics in the last 2 weeks. One wasn't effective against this strain, he was allergic to the second and now he has had another reaction to this one.