Corticosteroids are a type of anti–inflammatory medication that is effective in the treatment and prevention of allergic reactions and asthma attacks. While there are several types of corticosteroids, all work on the same principal – reducing or preventing inflammation. Most corticosteroids used to treat allergies and asthma reduce or prevent inflammation in the respiratory tract to relieve or avoid airway blockages.

Corticosteroids are considered the most effective medication currently available for the treatment of inflammation in the bronchial tubes. This drug type can be administered through several different methods. These include:

• Inhaled methods (e.g., inhalers, nebulizers). Medication is breathed deep into the lungs where it comes into contact with the mucous membranes of the lungs.

• Nasal sprays. Medication is inhaled into the nose and sinuses where it comes into contact with the walls of the sinuses. With this form of treatment the medication does not reach the lungs.
  
  
• Topical creams. Medication is applied directly to the skin to treat that skin area.
  
  
• Oral methods (e.g., pills, liquids). Medication is swallowed and absorbed into the bloodstream where it spreads throughout the body.
  
  
• Intravenous methods. Medication is injected under the skin through a needle and syringe. It enters the bloodstream and spreads throughout the body.

Inhaled corticosteroids are usually prescribed for the prevention of asthma or allergy symptoms. While most types of this medication have many side effects associated with them, inhaled and nasal spray corticosteroids usually affect only the inside of the lungs and sinuses, with very little of the medication penetrating into the bloodstream. This targeted delivery method is able to prevent many of the side effects experienced with more systemic forms of corticosteroids.

Oral and injectable forms of corticosteroids must travel throughout the entire body to reach problem areas. This allows the drug to come into contact with multiple organs and tissues in the body, making side effects more pronounced.  As a result, this form of corticosteroid is most suitable as a short–term or occasional therapy. However, some conditions (e.g., lung disease, severe chronic asthma) may warrant long–term corticosteroid use.

Corticosteroids work by mimicking the hormone cortisol, which the adrenal gland naturally produces to protect against illness. It is unclear how exactly corticosteroids are able to so effectively reduce inflammation, but studies have shown that the medications lower the amount of chemicals released by some inflammatory cells. This leads to decreased swelling in inflamed areas.

When used to treat allergies and asthma, corticosteroids decrease inflammation in the airways and reduce mucus production. This opens the airways, permitting more airflow and treating or preventing symptoms such as shortness of breath and difficulty breathing. Corticosteroids also keep the cells from responding to additional stimuli that may cause further inflammation. This reduction in hyperreactivity (excessive sensitivity) makes the medication useful as a preventative treatment.

Individuals should never stop taking a corticosteroid treatment abruptly as serious side effects can result. However, some physicians have recently begun to recommend corticosteroid treatments taken as–needed for the treatment of mild asthma. A physician can provide a schedule for safely discontinuing the use of corticosteroids.