I just had an appointment with my allergist today to discuss this. He's also thinking that food is not the cause. I'm going for a blood test -- thyroglobulin antibodies and thyroid peroxidase antibodies, if I'm reading his handwriting correctly. The test may show that I've developed antibodies to my thyroid, which apparently is a problem for some people. Or, it might show that we can rule that out, in which case...?

Also I'm going to get some Zirtec, to see if that works better than the Claritin that I've been taking so far.

The good news is that the last attack was not as bad as the one in July. I don't know if that's because I started taking all the antihistimines sooner, or I was just lucky.