Allergen immunotherapy can reduce symptoms of allergic rhinitis and asthma and decrease the need for medication, but it poses the risk of asthma exacerbation or anaphylaxis, particularly in patients with uncontrolled asthma.
Allergic rhinitis and asthma are both respiratory allergies that respond to allergen immunotherapy, or AIT, which was the focus of a review recently published recently published in Allergy. According to the review’s authors, AIT may be given subcutaneously or sublingually. Meta-analyses have shown that both methods of delivery can reduce the symptoms of allergic rhinitis and asthma as well as the need for medication.
Most clinicians no longer use intranasal and bronchial AIT because of their adverse effects. Like these delivery methods, subcutaneous and sublingual AIT may cause asthma exacerbation or anaphylaxis, particularly in patients with uncontrolled asthma, although sublingual AIT is less likely to do so than subcutaneous AIT. As a result, clinicians must carefully assess asthma status before initiating AIT.
Moreover, researchers have yet to identify the types of patients who are most likely to benefit from AIT. And because AIT products vary in quality, potency, and allergen content, their effects often differ.
Allergic rhinitis often precedes the development of asthma, which provides an opportunity to prevent asthma by treating rhinitis effectively. Along with being able to treat allergic rhinitis, AIT also appears able to prevent its progression to asthma. And because AIT is a systemic treatment, it treats the entire airway instead of just a specific part.
Furthermore, patients with allergic airways disease continue to benefit from AIT for some time after the last dose of allergen is given. And AIT may prevent patients with allergies from becoming sensitized to additional allergens.
The mechanisms by which AIT exerts its effects remain unclear. Laboratory studies have shown that AIT systemically modifies the type 2 immune response. Under the influence of AIT, the immune system synthesizes specific immunoglobulin G antibodies instead of inducing allergen-specific immunoglobulin E antibodies. By inducing regulatory immune responses, AIT exerts a sensitization-blocking effect. Studies have also shown that AIT reduces allergic inflammation in human nasal mucosa and mouse lungs.
Moreover, the immune systems of allergic asthma patients may recognize more allergens than those of patients who do no develop allergic asthma. As a result, introducing AIT early in the allergen sensitization process (ie, before patients are 2 years old) could reduce the risk of allergic asthma in young children at high risk for the disease owing to personal or family history of allergic disease.
The current evidence supporting the ability of subcutaneous AIT to prevent the development of asthma in children with allergic rhinitis is stronger than that for sublingual AIT. However, the Grazax Asthma Prevention Study may clarify whether sublingual AIT can prevent asthma in children with allergic rhinitis.