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Allergies Health Center

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Allergy Relief: Antihistamines vs. Decongestants

Antihistamines and decongestants won't cure your allergies. But they’ll give you much-needed relief for a runny or congested nose.

Antihistamines target histamine, which your body makes during an allergic reaction.

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You can take them as pills or in a nasal spray. 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 your symptoms, but they work best when you take them before you feel a reaction. They 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 these by mouth in pills or liquids, like pseudoephedrine.  Decongestants also come in nasal sprays, including oxymetazoline and phenylephrine. But if you use them too often, they can make your symptoms harder to treat.

Some medications combine antihistamines and decongestants. Their names usually end with “-D.” 

Do You Need a Prescription?

Some of these drugs need a prescription. Others don't. First try an over-the-counter brand. But check with your doctor or pharmacist to make sure you have the right medication for your symptoms. If you don't get relief, ask for something stronger.

What About Side Effects?

You shouldn’t drive when you take antihistamines such as brompheniramine (Dimetapp Allergy, Nasahist B), chlorpheniramine (Chlor-Trimeton), clemastine (Dayhist, Tavist), and diphenhydramine (Benadryl). They can make you drowsy. Others such as desloratadine (Clarinex), fexofenadine (Allegra), and loratadine (Alavert, Claritin) usually don’t.

Decongestants can also cause side effects, such as:

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

You shouldn’t take decongestants if you have high blood pressure or heart problems. If you have prostate problems that make it hard to pee, these drugs can make the problem worse.

Don’t use decongestant nasal sprays for more than 3 days in a row, as they may make your nasal congestion and swelling worse and last longer.

Check the drug label for more information about side effects.

WebMD Medical Reference

Reviewed by Stanley M. Fineman, MD, MBA on February 28, 2015

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