You are clearly in distress with the acute generalised urticaria and angioedema
episode and not helped by the fact that even prednisolone
is taking its time.
It is unlikely seafood allergy
as the reaction does not proceed for so long even though all of us think of an event as the trigger. Most allergists though would like to ensure you have a blood test
against the food panel that you had on the day and of course, shrimp crab lobster etc by a specific IgE blood test.
Skin testing would be required at a later stage (if blood tests are negative) and you are off all antihistamines for 2 weeks.
Saying that, I think all of them will be negative (i.e., no allergy) and at the same time you ought to get a blood test for CBC, LFT, creatinine
, Mast cell tryptase, IgE, TSH TPO antibodies as the 'urticaria' may have an autoimmune component.
Prednisolone is reserved for the end if antihistamines do not work, but ultimately all will work once this acute phase is over. If you have required 30-40mg for more than 10 days, it is best you slowly taper it down and stop at 6 weeks. By then, fexofenadine
180mg and hydroxyzine
25mg at night only would have started to work.
20% do not respond to several antihistamines, and would need steroid sparing agents that must be discussed in detail with your doctor.