Delayed reactivity does not show up on the traditional allergy tests (those tests only look for IgE antibody-mediated allergies)...suggest consulting an Integrative or Naturopathic Physician to test for IgG/IgA/IgM antibodies to foods. And make sure they do a total immuneglobulan panel as well (i.e., total IgG, total IgM, total IgA, total IgE), in case you have a deficiency that would affect the test results.
Yes, it is possible your high-histamine foods combined with the pollen allergies to create an "allergic overload." And some foods cross-react with pollens (especially some fruits/veggies & grains), too.
I agree your testing was done too close to taking antihistamines & steroids. It takes about a month for the Zyrtec type of antihistamine to fully exit the body (Benadryl takes about a week), and up to 6-12 months for steroids to exit the body.
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube
Meds: Flagyl, Domperidone, Zofran, Claritin, Andrographis & other herbs, homeopathy, supplements, etc.