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Decongestants and Antihistamines for the Common Cold

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While there's no cure for the common cold, there are cold medicines that can ease cold symptoms. When taking decongestants and antihistamines, it's important to know how they work to treat cold symptoms. It's also important to know who should -- and should not -- take decongestants and antihistamines.

Decongestants and antihistamines come in many forms (see table below), including as ingredients found in multi-symptom cold relief drugs. Decongestants are often found in daytime cold medicines because they may keep you awake. Antihistamines are frequently included in nighttime cold medicines as some can make you drowsy.

How Do Decongestants Work?

Decongestants help reduce swelling in the nasal passages, which relieves the feeling of pressure and improves airflow through your nose. In response to an allergen or the cold virus, the tissues in your nose swell and increase their production of fluid and mucus. As a result, you might feel fullness or pressure in your nose and head. That's congestion, and it can cause you to have trouble breathing through your nose. Decongestants reduce swelling and improve airflow to help you breathe through your nose.

Decongestants come in pill form or nasal sprays. Nasal sprays should be used for no longer than three days as you may have an increase in congestion if you take a nasal spray longer than that.

How Do Antihistamines Work?

Whether antihistamines are effective for relieving cold symptoms is unclear. But for some people, older types of antihistamines may help relieve sneezing and runny nose from a cold.

Antihistamines work by blocking histamine that is produced by the body in response to allergens or irritants. This histamine causes tissues in the nose to itch and swell. However, most experts say that histamine is not the major cause of the runny nose that is found with the common cold. But some of the older antihistamines, such as brompheniramine and chlorpheniramine, do seem to be effective at relieving cold symptoms. Their main side effect is drowsiness, which makes them difficult for some people to take during the day. That's why antihistamines are often included in nighttime cold medicines. Newer antihistamines like fexofenadine (Allegra) and loratidine ( Claritin) have not been shown to work against cold symptoms.

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