Delayed allergic reaction

Patient: My son is anaphylatically allergic to nuts(peanuts, almonds, cashews and walnuts) and accidently ate a very small amount of something which had peanuts in it approximately 48 hours ago, he had no symptoms of any reaction at the time but I did administer antihistamine as a precaution. He now is feeling sick and dizzy is it possible he is having a delayed reaction or is it just a coincidence and he is just coming down with the flu?

Symptoms: Lethargy, headache, dizziness temperature

Doctor: No, your son is not suffering from a delayed hypersensitivity reaction. Rather, his symptoms seem to be as a result of t he anti-histaminic medication that you gave him the day before. So don’t worry he should be fine in day or two.