Asthma is a chronic disease that affects the lungs. It is characterized by inflammation in the airways and causes symptoms like wheezing, chest tightness, shortness of breath and coughing. For many asthma patients, allergies are a major trigger for asthma symptoms. According to estimates, over 60% of adult asthma cases are allergy-induced. When asthma is triggered by allergies, it is called allergic or atopic asthma. In this article, we discuss the current state of therapeutics available for treating allergic asthma.

Pathophysiology of Allergic Asthma

Allergic asthma is an immune response triggered by exposure to common allergens like dust mites, pollen, mold, pet dander etc. These allergens are inhaled and recognized by the immune system as foreign bodies. This initiates a reaction involving immunoglobulin E (IgE) antibodies that attach to mast cells and basophils. On re-exposure to the same allergen, it binds to the IgE antibodies and causes the mast cells to degranulate. This releases inflammatory mediators like histamine, leukotrienes and cytokines that cause contraction of the airway smooth muscles leading to symptoms of bronchospasm, swelling of airways and excessive mucus production. Over time, this chronic inflammatory response can damage the airways and impair lung function.

Controller Medications for Long-Term Control

The mainstay of treatment for allergic asthma involves regular use of controller medications to reduce airway inflammation and prevent asthma exacerbations from occurring. Inhaled corticosteroids (ICS) are the most potent and effective class of controllers. Popular ICS medications include fluticasone propionate, budesonide and beclomethasone dipropionate. Long-acting beta agonists (LABA) such as salmeterol and formoterol are often used in combination with ICS to provide added bronchodilation. Combination inhalers containing both an ICS and LABA work synergistically to achieve better asthma control compared to either medication alone. Leukotriene receptor antagonists like montelukast are also used as alternate daily controllers. For severe asthma, adjunct medications like omalizumab (anti-IgE), mepolizumab and reslizumab (anti-IL5) have shown effectiveness by reducing airway eosinophilia. Adherence to controller therapy is crucial for gaining optimal benefit in managing symptoms and preventing exacerbations.

Reliever Medications for Symptom Relief

Short-acting beta agonists (SABA) like albuterol and levalbuterol are the standard reliever medications used on an as-needed basis for controlling asthma symptoms and reversing airflow obstruction during acute exacerbations. They work very rapidly, within 5-15 minutes, by relaxing airway smooth muscles. For quicker relief from asthma exacerbations, nebulized SABA therapy may be preferred over inhalers. A short course of oral corticosteroids should be used for worsening or uncontrolled symptoms despite optimal use of usual medications to prevent development of further deterioration and need for emergency care.

Allergen Avoidance Strategies

Avoiding exposure to known Allergic Asthma Therapeutics is another key component of asthma management, especially in conjunction with pharmacological therapy. Common allergen triggers should be identified through allergy testing. Then environmental control measures may include using mattress and pillow covers, HEPA filters and air purifiers to reduce dust mites and pet allergens. During high pollen seasons, keeping windows closed can help limit pollen exposure. Mold growth should be eliminated by keeping indoor areas dry. For food allergies like peanut, complete avoidance of the allergenic food item is recommended. With multi-allergen sensitivities, comprehensive environmental control tailored to individual patient needs can provide additive benefit to maximizing asthma control.

Allergen Immunotherapy

Allergen immunotherapy, also known as allergy shots or desensitization, involves administering gradually increasing doses of the specific allergen extracts through subcutaneous injections. This modifies the body's immune response over 3-5 years to become tolerant to the allergen and provides long-lasting relief even after discontinuation of therapy. Allergen immunotherapy is available for common inhaled allergens like dust mites, mold, pollen and some animal allergies. It has been shown to reduce symptom severity and medication requirements as well as lower the risk of developing new allergies later in life. For patients with significant impact on quality of life from allergies despite optimal medical and avoidance strategies, subcutaneous immunotherapy should be strongly considered. Newer sublingual (under the tongue) forms also have promising efficacy and convenience.

New Therapeutic Targets

Research into novel targeted therapies for allergic asthma aims at addressing key molecular pathways driving the disease. Drugs targeting IgE like omalizumab have already demonstrated clinical success. Other promising targets include blocking cytokines like IL-4, IL-5, IL-13 which mediate eosinophilic inflammation. Biologics that inhibit these cytokines have shown great potential, with FDA approvals for mepolizumab, reslizumab and benralizumab. Drugs targeting thymic stromal lymphopoietin activation of mast cells and type 2 helper T cells are under investigation. Next generation monoclonal antibodies with dual inhibition of IL-4 and IL-13 are entering Phase III trials. Small molecule drugs targeting Janus kinase (JAK) pathways are being studied for oral administration in asthmatics. These newer biologics and oral therapies could change the treatment paradigm for severe uncontrolled allergic asthma. Overall, targeted immunotherapy approaches hold promise to deliver safer and more effective management in future.

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