Antihistamines work by blocking the effects of histamines, which help with symptoms such as: Benadryl and Claritin are antihistamines. Benadryl contains the active ingredient diphenhydramine. It is a ...
Claritin-D, Allegra-D, and Zyrtec-D all contain a decongestant called pseudoephedrine, the same active ingredient that powers Sudafed. It makes your nose feel less stopped up by narrowing the ...