Most people who struggle with inhalant allergies are familiar with the stuffy nose, clogged sinuses, and mounting pressure in the head that can signal an allergic episode. In fact, studies show that patients consider nasal congestion to be one of the most bothersome symptoms of allergic rhinitis (allergies that primarily affect the nose and sinuses). Nasal congestion affects sleep, productivity, and quality of life.

While antihistamines or corticosteroids may help prevent the worst of these symptoms, sometimes it’s necessary to take additional medications to relieve increasing pressure on the sinus cavities and promote the drainage of excess mucus. Decongestants are over-the-counter medications that help break the cycle of congestion and mounting pressure.

Examples of common decongestants include pseudoephedrine (e.g., Sudafed), phenylephrine, and phenylpropanolamine. Although these common over-the-counter drugs can bring temporary relief from congestion, they don’t treat the underlying cause of allergies; they merely offer relief from one of the more problematic symptoms of common inhalant allergies.

Decongestants work by prompting blood vessels to constrict, helping to relieve congestion caused by the dilation of blood vessels in the nasal passages.

Although decongestants are relatively inexpensive and readily available, they’re more difficult to obtain than, say, over-the-counter antihistamines. Unfortunately, pseudoephedrine is a raw material used in the illegal manufacture of the dangerous street drug, crystal methamphetamine.

In an effort to limit the damage to communities caused by the manufacture, sale, and abuse of this drug, congress passed the Combat Methamphetamine Epidemic Act of 2005, which was signed into law by President George W. Bush in 2006. The law strictly regulates the sale of pseudoephedrine, pseudoephedrine-containing products, and phenylpropanolamine. Many states have also enacted sales restrictions. Typically, the medications must be obtained directly from a pharmacist, after showing a valid driver’s license and providing a signature. Quantities available for sale per visit are also limited.

Side Effects and Limitations

Decongestants such as pseudoephedrine are stimulants, so potential side effects include anxiety, insomnia, restlessness, dizziness, and high blood pressure (hypertension). In rare cases, pseudoephedrine use may be linked to an abnormally rapid pulse, or palpitations (irregular heartbeat). Some people can use decongestants with no noticeable side effects, but people with type 2 diabetes, hypertension, hyperthyroidism, closed angle glaucoma, or heart disease are cautioned not to take these drugs except under a doctor’s supervision. Pregnant women should also avoid pseudoephedrine.

Unless formulated for extended or controlled release, pseudoephedrine is ordinarily taken once every 4-6 hours, ideally for no more than one week at a time. People who are taking any drug from a class known as monoamine oxidase inhibitors (MAOIs) should not take decongestants. Certain other drugs, such as the antibiotic linezolid (Zyvox), may also cause a serious drug interaction; consult with your physician before taking a decongestant if you are currently taking any other medications.

Nasal Spray Decongestants

Most people take decongestants orally, in the form of a pill. Nasal sprays featuring a decongestant that is delivered directly into the nasal cavities offer an alternative to this “systemic” delivery. These products should never be used for more than three to five days in a row, however. 

Although they may provide temporary relief from congestion, this form of decongestant delivery is especially prone to inducing tolerance for the drug, and may result in “rebound” congestion that leaves the user feeling worse than when he started. Examples of these topical decongestant nasal sprays include oxymetazoline (Afrin), phenylephrine (Neo-synephrine), and pseudoephedrine (Sudafed). 

Controlled studies have shown that the combination of an antihistamine drug and a decongestant is better at relieving the symptoms of allergic rhinitis due to seasonal inhalant allergies (“hay fever”) than either of the individual drugs taken alone. Although these drugs only offer symptomatic relief, and should be used with some caution, they can be an important weapon in the ongoing battle against the misery of allergies.