Allergies Health Center

Antihistamines or Decongestants? Getting Allergy Relief

Antihistamines and decongestants won't cure your allergies, but when you've got a runny or congested nose, they're two of the most widely used types of medicine people use.

Antihistamines target a chemical called histamine, which your body makes when you have an allergic reaction.

You can take antihistamines as pills or nasal sprays. The pills target itching, sneezing, and runny nose. The nasal sprays work on congestion, an itchy or runny nose, and postnasal drip.

Antihistamines can ease symptoms once you have them, but they work best when you take them before you feel allergy symptoms. Taken regularly, antihistamines can build up in your blood to protect against allergens and prevent the release of histamines. Ask your doctor if you should start taking allergy medicine a couple of weeks before you usually have symptoms.

Decongestants cut down on the fluid in the lining of your nose. That relieves swollen nasal passages and congestion.

You can take decongestants by mouth in pills or liquids, or by nasal spray. Common decongestants include pseudoephedrine and phenylephrine.

Some medications combine antihistamines and decongestants. For example, Allegra-D, Claritin-D, and Zyrtec-D combine an antihistamine with the decongestant pseudoephedrine.

Do You Need a Prescription?

Some antihistamines and decongestants need a prescription. Others don't. You could first try a nonprescription medicine and if you don't get relief, check with your doctor to see if you need a prescription.  

Even if you take something that doesn't require a prescription, you should let your doctor know what you're taking. They can check that you've got the right medication for your symptoms, and check on side effects.

What About Side Effects?

Older antihistamines such as Benadryl (diphenhydramine) and Chlor-Trimeton (chlorpheniramine) can make you drowsy. The newer antihistamine Zyrtec (cetirizine) may also cause drowsiness.

Antihistamines such as Allegra (fexofenadine) and Claritin (loratadine) do not usually make you drowsy.

Decongestants can cause:

• Nervousness
• Sleeplessness
• Increased heart rate
• Increased blood pressure

Don’t use decongestant nasal sprays for more than three days in a row as they may worsen your nasal congestion and swelling.

Always check the drug label for more information about side effects.