Corticosteroids have a significant role in the management of allergies due to its broad anti-inflammatory action, which reduces the immunological response in allergic diseases. This is invaluable in the long term management of allergic diseases. Corticosteroids reduce the duration and severity of acute exacerbations in chronic allergic diseases like allergic rhinitis.
Anti-allergic Actions of Corticosteroids
Corticosteroids considerably reduce the manifestations of inflammation associated with an allergy. This is primarily due to its intense effects on the inflammatory cells and suppressive effects on the mediators of allergic response.
Following administration of a corticosteroid, the following effects are seen :
- decrease the concentration of eosinophils, basophils, monocytes and lymphocytes.
- decrease the migration of neutrophils from the blood vessels to the site of inflammation, thereby reducing the intensity of the inflammation associated with allergy.
- suppression of mast cell degranulation.
- reduces the release of histamine from basophils and mast cells.
- reduce the ability of immune cells to respond to antigens.
Corticosteroids can also affect the inflammatory response by reducing the prostaglandin and leukotriene synthesis by the action on the enzyme phospholipase A2. Prostaglandin synthesis is also decreased by the reduction in expression of cyclooxygenase-2 enzyme in inflammatory cells.
Corticosteroids and Different Allergic Diseases
Allergic Bronchial Asthma
Regular administration of corticosteroids decreases the bronchial reactivity to allergens and reduces the frequency of asthma attacks. Corticosteroids are primarily used to prevent asthma attacks. It has a minimal role in reversal of symptoms of acute asthma attacks.
Corticosteroids inhibit the migration of eosinophils, and mast cells to the airway and reduces the inflammation of the bronchial mucosa. Patients with mild to moderate asthma benefit from low dose inhaled steroids which are available in metered-dose inhalers. Those used in asthma include :
Use of inhaled steroids effectively avoids the systemic adverse effects of corticosteroid therapy seen with oral or parenteral corticosteroids. Use of inhaled corticosteroids are also safe in children. In severe acute attacks of asthma not responding to bronchodilators and inhaled steroids, intravenous corticosteroids like methylprednisone or hydrocortisone may be used to overcome the acute phase. Oral prednisone may be used occasionally for maintenance in refractory patients with severe asthma.
Intranasal corticosteroids are the treatment of choice and include steroids like :
A combination of intranasal corticosteroids and antihistamines is found to be effective in the treatment and management of allergic rhinitis. Intranasal corticosteroids have been found to provide significant symptomatic improvement. Application of nasal corticosteroids reduces itching, nasal discharge, sneezing, and nasal congestion. Intranasal corticosteroids can cause some topical side effects like local irritation, an unpleasant taste, and sometimes bleeding from nose (epistaxis).
Corticosteroid topical applications have been the one of the most important group of drugs used in ocular allergies including allergic conjunctivitis. The currently available corticosteroids for ocular use include :
Severe symptoms of urticaria may require the use of systemic corticosteroids like prednisone for symptomatic relief. Topical corticosteroids are used with significant improvement in conditions like allergic contact dermatitis. Corticosteroids are also useful in allergic conditions like drug and food allergies.
Corticosteroids (prednisone orally or methylprednisone / hydrocortisone intravenously) may help to prevent the late phase of anaphylaxis. However, corticosteroids are unlikely to produce beneficial effects in the acute stage. Intramuscular adrenaline is the treatment of choice in anaphylaxis. It is a physiological antagonist of histamine and reverses the effects of histamine.