When i go for first time allergy testing, do i need to fast? is it ok to take allegra (fexofenadine) for my allergy symptoms or not yet?

Antihistamine & test: No need to fast, but for skin testing you need to be off antihistamines for five days.

Dr Ali and another doctor agreed

No : If one is getting allergy skin testing done then one must refrain from using antihistamines for several days prior to testing. If one is getting allergy blood testing done then no need to avoids antihistamines. Fasting is not required prior to allergy skin testing or blood testing.

Test preparation: Since you are being treated for a low Vitamin D level, your physician may be ordering blood work at the same time. If you are having your blood drawn, I would suggest asking the technician about fasting. If you are scheduled only for skin allergy testing, you do not need to fast. You should not take antihistamines prior to allergy skin testing.