Several types of side effects are common with decongestant use. These are not usually a cause for concern. However, if these side effects worsen or become problematic, patients should contact a physician.

Decongestants are chemically related to the hormone adrenaline, the natural decongestant in the body that is also a stimulant. As a result, decongestants often make people feel jittery, nervous, excitable or restless. People who use these medications also may experience a blood pressure increase and insomnia.

Other side effects associated with decongestants include:

• Difficulty urinating in men (due to enlarged prostate gland)
• Dizziness and drowsiness
• Dry or irritated nose and nosebleeds
• Headache
• Loss of appetite

More serious side effects are occasionally experienced with decongestants. Patients experiencing these side effects should immediately inform their physician:

• Palpitations (rapid, irregular beating of the heart)
• Hallucinations
• Weakness
• Tremors (shaking or trembling)
• Seizures
• Very high blood pressure

In addition, some people may be at increased risk of a stroke (an event in which blood flow to the brain is restricted) when taking oral decongestants. Although the U.S. Food and Drug Administration (FDA) determined in 2000 that the ingredient phenylpropanolamine is not safe for use, people may still have expired decongestants at home that contain this substance. Phenylpropanolamine constricts blood vessels and also acts as a stimulant. It has been linked to an increased risk of hemorrhagic stroke (bleeding in the brain) in certain patients.

It is extremely important not to exceed the recommended dosage of any over-the-counter or prescription decongestant. One of the most commonly experienced side effects results from overusing decongestant nasal sprays. Rebound congestion (rhinitis medicamentosa) occurs when a decongestant nasal spray is used for too long (usually longer than three to five days). The condition is characterized by nasal swelling and congestion, which can make the condition difficult to detect as these are often the same symptoms that are being treated. To avoid rebound congestion, individuals using nasal spray decongestants should closely follow the directions on the label and discontinue use after several days, as directed.