What to expect at first visit to an allergist?

I am scheduled to see an allergist on Monday and I am fighting a terrible cold right now. Will that be a problem?
I have not taken antihistamines all week, as per the doctor's instructions, but I have caved-in and take a decongestant just to get some sleep for a couple of nights.

Did the doctor say not to take decongestant, or only antihistamines? I have no idea whether it will matter to them. I think the cold might interfere with their ability to get a good read on your symptoms, BUT the first meeting is likely to include a lot of questions for you to answer about symptoms when you aren't sick, as well as possibly a scratch test. I have had allergists meet with me once to get a feeling for what's going on, then schedule scratch tests for a later date. But I've also had an allergist give me the scratch test on the spot. Depends how busy their schedule is, I guess.

And I don't think the cold would interfere at all with scratch tests, which are done on the skin. But I am not sure how much it will get in the way if they are peering up your nose or listening to your lungs.