Decongestants and Antihistamines

What are decongestants and antihistamines?

Decongestants relieve a stuffy nose. Antihistamines help dry up a runny nose. These medicines are often confused with each other because they are both often used to help runny, stuffy noses. However, they are different and do not act the same way on your body.

Many nonprescription cold and allergy products contain several types of medicines. They may treat many symptoms. It can be confusing trying to figure out which medicine to choose. Ask your pharmacist or health care provider if you are not sure which medicine is best for your symptoms.

How do they work?

Decongestants narrow the blood vessels in the nose. This reduces swelling. It also reduces the amount of mucous made by your nose. You can buy some decongestants without a prescription. The most common types are:

pseudoephedrine (Sudafed)
phenylephrine (Neo-Synephrine).

Antihistamines block the effect of histamine. This is a chemical your body makes when you have an allergic reaction. It causes redness and swelling. Common antihistamine medicines are:

diphenhydramine (Benadryl)
chlorpheniramine (Chlor-Trimeton)
cetirizine (Zyrtec)
fexofenadine (Allegra)
loratadine (Claritin)
desloratadine (Clarinex).

When are they used?

Decongestants are often used to treat:

colds
ear or sinus infections.

Antihistamines are most often used to treat symptoms of allergies. These include:

sneezing and runny nose from hay fever
itching, swelling, and redness from hives or other allergic rashes.

What should I watch out for?

Decongestants

If used for too long, decongestants can make your stuffy nose worse instead of better. They make your blood vessels smaller so you should not take a decongestant if you have:

heart disease
high blood pressure
glaucoma
thyroid disease
trouble urinating or an enlarged prostate
asthma
diabetes.

Antihistamines

A common side effect of antihistamines is drowsiness. Some types are less likely than others to make you drowsy.

Taking antihistamines with other medicines, such as antidepressants or sedatives, may cause problems. Read the labels carefully. Ask your provider or pharmacist if you have any questions.

If you are pregnant, talk with your health care provider before taking these medicines.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File MED4261F.HTM Release 9.0/2006