I took sulfasalazine for 5 weeks and then broke out in a rash similar to what you're experiencing, but it was all over my body. It was a definite sulfa allergy and I was told never to take a sulfa drug again. I never used to be allergic to sulfa, and in fact had taken bactrim for chronic UTIs as a kid for several years. My rheumy said a sulfa allergy can develop at any point. I didn't get a chance to read all of the posts to this thread, so if this has been said please forgive me, but if you haven't mentioned this rash to your rheumy, please do so. If it is a sulfa allergy, then you need to stop taking the SSZ immediately. I almost ended up in the hospital with this rash.
I hope you feel better soon,
Current dx: Rheumatoid Arthritis
Suspected dx: UCTD/Early Lupus
Current Meds: Enbrel, Plaquenil, Aciphex, Ultracet, Zyrtec, Allavert-D, Zantac, Tylenol PM
Past Meds: Relafen, Vioxx, Mobic, Voltaren, Sulfasalazine, Entocort, Prednisone, Humira, Reglan