Benadryl Plus Capsules Benadryl Plus is a unique remedy that combines an antihistamine with a decongestant to relieve all your allergy symptoms in one powerful capsule: Pseudoephedrine Hydrochloride: A decongestant that relieves nasal & sinus congestion. Acrivastine: An antihistamine that helps relieve allergy symptoms such as sneezing, runny nose & watery eyes. Benadryl Plus Capsules get to work in just 15 minutes to relieve the symptoms of hayfever & pet, dust & skin allergies for up to 8 hours.