Fast effective relief from allergies.Lasts 8 hours.Active in 15 minutes Relief from allergy symptoms, including hay fever, dust allergy, pet allergy, skin allergies This medicine also provides relief from the symptoms of urticaria (hives and itchy skin rash).Benadryl Allergy Relief BENADRYL® Allergy Relief is the fastest-acting allergy relief capsule, it is the only brand to contain acrivastine a unique active ingredient. Acrivastine starts to work in 15 minutes providing fast relief. It can also be taken as required (up to three times per day) so that you can take as and when you need. This flexible dosing makes it suitable for dust and pet allergy sufferers who have short-lived allergy attacks, and for hay fever sufferers as it can be taken in the morning and evening when pollen is at its peak.