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

• Elevated blood pressure
• Dizziness and drowsiness
• Dry or irritated nose and nosebleeds
• Headache
• Loss of appetite
• Sleep disturbance
• Nervousness
• Restlessness
• Excitability

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

• Palpitations (an awareness of a strong, fast, irregular, abnormal or "galloping" heartbeat)
• Hallucinations
• Weakness
• Tremors (shaking or trembling)
• Seizures
• Very high blood pressure

In addition, some people may be at increased risk of stroke (an event in which blood flow to the brain is restricted) when taking oral decongestants. Some decongestants may contain phenylpropanolamine, a substance that constricts blood vessels and also acts as a stimulant. This substance has been linked to an increased risk of hemorrhagic stroke in certain patients.

It is extremely important not to exceed the dosage of any OTC or prescription decongestant. One of the most commonly experienced side effects results from the overuse of 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.

Patients should contact their physician if there are any questions on dosage or potential side effects.