Asthma affects more than 200 million people worldwide. The condition is more common in children than adults. Allergen exposure is a major trigger of exacerbations for many patients with asthma. Allergic asthma is characterized by symptoms that are activated by an allergic reaction.

Allergic asthma is the most common asthma. About 90 per cent of kids with childhood asthma have allergies, compared with about 50 per cent of adults.

Allergy triggers, such as pollen, mites, or moulds bring on the asthma symptoms associated with allergic asthma. Approximately 75-85 per cent of patients with asthma have positive immediate skin test results. 

Hence, management of allergies is the cornerstone of asthma management. An intensive indoor environmental control programme is recommended for patients with allergy-mediated asthma. Physicians who are treating asthma should be aware that patients who require daily asthma medication should be referred to an allergist. The form of hypersensitivity associated with asthma is described as immunoglobulin E (IgE)– mediated, or immediate as in the case of asthma exacerbation brought on in an allergic patient on exposure to the allergen he is sensitized to. 

The most common perennial allergens come from dust mites, cats, dogs, cockroach and fungal moulds. Asthma symptoms may also coincide with the pollination season of a tree, grass, or weed. In India, parthenium is a major outdoor aeroallergen. In most allergic patients, exposure and symptoms are perennial. Consequently, many patients who are allergic to common indoor allergens are not aware of the role of allergen exposure in their disease.

Allergen avoidance and other environmental control efforts are feasible and effective. Eliminating even one of many allergens can result in clinical improvement.

The National Asthma Education and prevention programme (NAEPP) Expert Panel guidelines for the management of asthma recommend that patients who require daily asthma medications have allergy testing for aeroallergens, including perennial indoor allergens. Immediate (IgE-mediated) hypersensitivity can be demonstrated by skin testing or blood testing with aeroallergens.

Treatment focused on controlling the allergic component depends on education about avoiding allergen exposure. Physicians should consider the potential benefits and the ability of the patient to comply when deciding whether to recommend this approach. 

The avoidance measure should be allergy-specific, communicated effectively and time-bound. Immunotherapy Allergen immunotherapy should be considered only if specific allergens have a proven relationship to symptoms; the individual is sensitized (i.e., positive skin test or RAST findings); the allergen cannot be avoided and is present year-round (e.g., occupational); or symptoms are poorly controlled with medical therapy.

This treatment is especially useful if asthma is associated with allergic rhinitis. Allergen-specific immunotherapy is aimed at modifying the natural history of allergy by inducing tolerance to the causative allergen. In its traditional, subcutaneous form, immunotherapy has complete evidence of efficacy in allergic asthma. Sublingual Immunotherapy is the method of allergy treatment that uses an allergen solution given under the tongue, which over the course of treatment reduces sensitivity to allergens. Sublingual immunotherapy, or SLIT, has a very good safety profile and is given at home in adults and children.