Benadryl Allergy Relief Capsules Benadryl Allergy Relief Capsules start to work in just 15 minutes to relieve the symptoms of hayfever & other allergic conditions such as pet & dust allergies for up to 8 hours, so you can get on with your day. They contain the antihistamine acrivastine that helps relieve allergy symptoms such as sneezing, runny nose & watery eyes. Benadryl Allergy Relief Capsules can also be used to treat the symptoms of urticaria, also known as hives, where the skin looks blotchy with white raised wheals (bumps) surrounded by redness. Benadryl Allergy Relief Capsules can be used by adults under 65 years old & children aged 12 years & over.