Decongestants and Antihistamines for a Cold

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 medicines. Decongestants are often found in daytime cold medicines because they may keep you awake. Antihistamines are frequently included in nighttime cold medicines as they make most people 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 so you can breathe through your nose.

Decongestants come in pill form or nasal sprays. Nasal sprays should be used for no longer than 3 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 many people, antihistamines may help relieve sneezing and runny nose from a cold.

When your nose and sinuses are affected by a cold virus, special cells in your nose and sinuses release a chemical called histamine. Histamine causes the tissues in your nose to itch and swell and to alter the mucus it secretes so that the mucus becomes clear and runny.

Antihistamine cold medicines block histamine from interacting with the nasal tissues, thus preventing sneezing and runny nose.

Only the older antihistamines, such as brompheniramine and chlorpheniramine, are 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 Allergra and Claritin have not been shown to work against cold symptoms.

Are decongestants and antihistamines unsafe?

The decongestant phenylpropanolamine, or PPA, was used for years as an ingredient in many cold medicines to relieve stuffy nose and congestion. This decongestant was also used in diet pills to control appetite. In 2000, PPA was linked to a significantly increased risk of stroke, especially in women aged 18 to 49. As a result, the FDA in November 2000 banned the use of PPA in all prescription and over-the-counter medicines.

Newly manufactured decongestants and cold medicines do not contain PPA, but you should make sure you don't have any old cold medicines in your medicine cabinet that might contain the ingredient. Be sure to clean out your medicine cabinet and discard all old medicines.