US National Library of Medicine
Medline Plus: Pseudoephedrine
Here, you can read detailed notes on pseudoephedrine, a main ingredient in many over-the-counter and prescription decongestants. This website provides responses to several questions concerning this medication including: "How should this...
Other
Allergy Glossary: Antihistamine
This website provides a brief definition of "Antihistamine," and lists several examples of this type of drug.
Other
Allergy Glossary: Decongestant
This is a very brief write-up about decongestants, where you can read about how this medication can relieve congestion and how they can also cause adverse side effects.