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How Do Decongestants Work?

During an allergic reaction, tissues in your nose may swell in response to contact with the allergen. That swelling produces fluid and mucous. Blood vessels in the eyes can also swell, causing redness. Decongestants work by shrinking swollen nasal tissues and blood vessels, relieving the symptoms of nasal swelling, congestion, mucus secretion, and redness.

What Are the Side Effects of Decongestants?

Decongestants may raise blood pressure, so they typically are not recommended for people who have blood pressure problems or glaucoma. They may also cause insomnia or irritability and restrict urinary flow.

Combination Allergy Drugs

Some allergy drugs contain both an antihistamine and a decongestant to relieve multiple allergy symptoms. Other drugs have multiple effects aside from just blocking the effects of histamine, such as preventing mast cells from releasing other allergy-inducing chemicals.

Some examples of combination allergy medicines include:


Steroids, known medically as corticosteroids, can reduce inflammation associated with allergies. They prevent and treat nasal stuffiness, sneezing, and itchy, runny nose due to seasonal or year-round allergies. They can also decrease inflammation and swelling from other types of allergic reactions.

Systemic steroids are available in various forms: as pills or liquids for serious allergies or asthma, locally acting inhalers for asthma, locally acting nasal sprays for seasonal or year-round allergies, topical creams for skin allergies, or topical eye drops for allergic conjunctivitis. In addition to steroid medications, your physician may decide to prescribe additional types of medications to help combat your allergic symptoms.

Steroids are highly effective drugs for allergies, but they must be taken regularly, often daily, to be of benefit -- even when you aren't feeling allergy symptoms. In addition, it may take one to two weeks before the full effect of the medicine can be felt.

Some steroids include:

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