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What is IgE mediated asthma
IgE mediated asthma, also known as allergic asthma, is the most common form of asthma. In allergic asthma, the body initiates an immune response against an allergen which results in the production of IgE antibodies. The most common allergens are pet dander, dust mites, mold and pollen.
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Most of the allergens are proteins which cross the epithelial cell barrier of the lungs. These allergens stimulate the immune cells of the body to produce IgE antibodies. This process stimulates the release of a number of mediators like histamine, tryptase, leukotrienes, cytokines and tumor necrosis factor. These mediators cause airway inflammation. This inflammation produces airway muscle hyperresponsiveness, collection of fluid and mucus production which increases the work of breathing. It has been suggested by the hygiene hypothesis that early exposure to infections and allergens might protect against asthma in later life because of improved immune system. Breastfeeding also protects against development of allergic asthma.
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The following are the clinical features of asthma:
- Tachypnea (Increase in rate of breathing)
Aggravating factors of asthma
- Pet dander
- Molds and pollen
- Tobacco smoke
- Weather changes
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- Complete blood count - To rule out any infection
- Arterial blood gas analysis
- Serum electrolyte level
- Chest radiography
- Allergy testing
- Exercise tolerance testing
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Management and treatment
An acute attack of allergic asthma is a medical emergency and should be dealt with accordingly. The attack may be mild or severe. The following comprise the immediate management of allergic asthma:
- Provide oxygen during transport
- Cardiorespiratory monitoring
- Pulse oximetry
- Nebulization with beta agonist like albuterol or ipratropium bromide
- Oral or intravenous steroids like dexamethasone or prednisolone, depending on severity of attack
The next line of management involves preventing or reducing the severity of attacks of asthma. It involves:
- Inhaled drugs like albuterol, salmeterol, levalbuterol and ipratropium whichrelieve the bronchospasm. Inhalation of these drugs by a metered dose inhaler at the start of an attack aborts the attack by relieving the bronchospasm and prevents it from becoming severe.
- Other drugs used are terbutaline and theophylline.
- Mast cell stabilizers like cromolyn sodium help in stabilizing the mast cells and prevents the release of histamine.
- Leukotriene receptor antagonists like zafirlukast and montelukast can also be used to prevent attacks of asthma.
- Other drugs which can be used are inhaled corticosteroids like budesonide.
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Follow up and prevention
Regular follow up of asthmatic patients is necessary to assess the severity or progression of disease.
Prevention of further attacks forms an integral part of management of these patients. This involves prompt treatment of infections, reduced exposure to allergens and tobacco smoke, reduce humidity by dehumidifier to prevent growth of molds and immediate recognition of an attack to prevent it from becoming severe.
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1. Allergic diseases: diagnosis and management, 1997 by Roy Patterson, Leslie Carroll Grammar, Paul A Greenberger.
2. Manual of clinical problems in pulmonary medicine, 2005 by Richard A Bordow, Andrew L Ries, Timothy A Morris.