Histamine is released by your body as part of an allergic reaction. It can cause redness, swelling, itching, a runny nose and watery eyes, among other things. Antihistamines work by preventing the effects of histamine. They come in tablets, capsules, sprays, liquids injections or creams. Allergies and colds often cause stuffy noses.
Decongestants work by narrowing blood vessels.
This relieves nasal congestion. The main airways between your throat and lungs are called bronchi. In asthma, inflammation causes the bronchi to become twitchy or extra-sensitive. Anti-inflammatory medications reduce inflammation in the airways. They include cromolyn, nedocromil, anti-leukotrienes and corticosteroids.