Reading your symptoms and that you are unable to stop the antihistamines even for 48 hours for a skin test, sounds unlike allergy to known triggers.
If the hives has not started after starting a new medication (i.e, antibiotics or pain killers or aspirin
), you most likely have urticaria
(idiopathic) and will eventually respond to long-acting high-dose antihistamines.
Suggest continuing the allegra
180mg at morining and adding cetirizine
10mg lunch-time and evening. Usual treatment duration: 3 months without an attack.
Common avoidable triggers: alcohol, pain killers like opiates, NSAIDs (brufen etc), scratching (physical) or heat.
I hope this will be helpful.