Let's diagnose the doctor!

I have a mysterious ailment that's driving me crazy. On Tuesday morning, I woke up with an itchy rash all over my arms. On Wednesday, it was itchier and starting to spread to my face. On Thursday, my ears were swollen and the rash was all over my face and neck. On Friday my face started to swell. It's even worse today, with the rash covering my arms, neck (front and back), and face.

By Thursday I was so miserable that I went to a pharmacy. In France, you can often get fairly strong drugs OTC, so a pharmacy is the first logical stop. The pharmacist took one look at me and sent me to the doctor down the street. She was kind enough to squeeze me in without an appointment--and for the standard fee of 23 Euros (French citizens get this fee reimbursed).

She said it definitely looks like an allergic reaction of some kind. But the cause had us scratching our heads--me literally! I have no known allergies at all. Some possibilities we discussed:

Sun allergy? Maybe, but the rash appeared after several days of rainy weather; we went swimming Saturday afternoon and then didn't see the sun again until late on Tuesday after my rash had already appeared.

Food allergy? I couldn't think of anything I ate that was unusual or new, and I've never been allergic to anything ever. Of course, food allergies can appear out of the blue.

Other chemical/agent? I did try one perfume on Monday afternoon on one of my hands, but the pattern of the rash doesn't point to perfume as a culprit. Basically my rash is everywhere the sun hits, if I were wearing pants and a short-sleeved shirt. I also wondered if I were reacting to something the sheets were washed in, since I put a new set of sheets on over the weekend. This might explain the rash's location, since I wear long pants and a short-sleeved shirt to bed.

The doctor prescribed an antihistamine (5 mg desloratadine daily for 2 weeks). So far my rash has continued to get worse even with the medication. I bought a hydrocortisol cream yesterday and have been applying it in the evenings. Not sure if it helps. 

This brings me back to the first hypothesis of a sun allergy, with the laundry detergent being a second runner-up. The pattern of the rash is strikingly correlated to where my shirtlines fall. But it would have to be a photoallergic eruption--a delayed reaction caused by a combination of a drug/medication and sun exposure--not a polymorphus light eruption because PMLEs occur almost instantly after sun exposure.

Remember, I hadn't seen the sun for about 2 1/2 days when my rash broke out. I wonder if it might be the sunscreen I used on Saturday afternoon. My sister brought a bottle to the beach, and I think I used hers instead of mine. I also have a small sample-sized bottle that I used at some point last week when I forgot my larger bottle. That would make sense why my rash is where it is, and why it didn't show up for a few days after the sun exposure.

I also changed the sheets on our bed and washed the new ones in different detergent--one I've been using on my own clothes that doesn't seem to bother me.

Tomorrow I am going to do an experiment to test my photoallergy hypothesis: draw 3 large circles on my lower legs and apply each of the 3 different kinds of sunscreen in our apartment, then sit in the sun for 15-20 minutes. If, in a day or two, I develop a rash, I'll have solved this mystery illness.

In the meantime I feel like a clown with my bright red face and swollen ears. An itchy, miserable clown.

So, what do you think? Any other unexplored possibilities? 
.