Atopic Triad

Atopy refers to the genetic predisposition to developing allergic conditions, such as atopic dermatitis, allergic asthma, allergic rhinitis, and food allergies. Individuals with one atopic condition are at higher risk of developing another one. Additionally, individuals with a family history of atopic conditions are at higher risk of developing allergic disease.  

Atopic conditions result from an increased inflammatory response after exposure to allergens, including environmental factors like dust mites, pollen, animal hair, and food. Clinical manifestations of atopy usually appear early in childhood and can persist for years or decades. Nonetheless, they might resolve spontaneously with increasing age. The progression of atopic manifestations from atopic dermatitis to asthma and allergic rhinitis during childhood is commonly described as “atopic march.” 

The atopic triad is a term used to describe the coexistence of atopic dermatitis, also known as eczema; asthma; and allergies, like allergic rhinitis and conjunctivitis, also known as hay fever.  

Atopic dermatitis is an allergic skin condition that usually occurs due to an increased immune response to a variety of potential allergen triggers, such as pollen or dust mites. Individuals with atopic dermatitis typically have rashes or scaly patches. The rash might be present on the face, scalp, and flexor surfaces of the extremities, which include the creases of the wrists, elbows, and knees. The rash usually includes intermittent patches of red itchy skin that can occasionally blister and peel, compromising the skin barrier. Eczema treatment can include avoiding triggers, which can be identified through skin testing or allergen-specific IgE testing; frequent moisturization; topical steroids, like hydrocortisone; and topical calcineurin inhibitors, such as tacrolimus and pimecrolimus. 

Asthma is an obstructive lung disease characterized by chronic inflammation, narrowing of the airways and more difficulty breathing. Individuals with asthma can have asthma exacerbations, or attacks, usually triggered by environmental irritants. Subsequently, the immune system generates inflammation in the lungs, which can cause the airways to become even narrower and filled with mucus, which can be life-threatening. Asthma attacks can present with coughing, chest tightness, dyspnea, difficulty breathing, and wheezing, which sounds like high-pitched whistling. There are various treatment methods, including avoiding the triggering allergen if possible. Medications can also be used and may include a short-acting beta agonist, like albuterol, which acts as a bronchodilator to widen the airways; long-acting beta-agonist, like salmeterol; and inhaled and oral corticosteroids, such as fluticasone, which work as anti-inflammatory medications. In severe asthma exacerbations, nebulized bronchodilators like ipratropium and systemic corticosteroids, like prednisone, are usually given to rapidly decrease inflammation and open up the airways. In cases where asthma is not well controlled with standard inhalers, treatment may include monoclonal antibodies, which are medications that target specific molecules involved in the immune response that causes airway inflammation. Examples include omalizumab, mepolizumab, and dupilumab.  

Allergic rhinitis is a nasal inflammation typically caused by airborne allergens, like pollen, dust, animal hair, or mold spores. These allergens cause mast cells in the tissues to release histamine, causing inflammation of the eyes and nose. Symptoms of allergic rhinitis include frequent bouts of sneezing, rhinorrhea (i.e., runny nose) and nasal itching. Additionally, allergic rhinitis can be associated with allergic conjunctivitis, which presents with red, itchy, and watery eyes. In terms of treatment, intranasal sprays of antihistamines, like azelastine; or corticosteroids, like betamethasone, can be used to relieve the congestive symptoms of allergic rhinitis. Nasal irrigation to flush the sinuses can also be used. For conjunctivitis, antihistamine eye drops like azelastine; steroid eye drops, like loteprednol or rimexolone;  cool compresses; and artificial tears, can be used. 

Although the exact mechanism is not entirely clear, atopy is associated with a genetic predisposition to developing an enhanced immune response against specific allergens, thereby causing conditions like eczema, allergies, and asthma.  Environmental triggers include animal dander, latex, pollen, and insect stings. Viral infections and foods, like nuts, shellfish, and eggs, are also common allergens.  

In general, allergic reactions occur in two steps. First, exposure to the allergen causes allergen-specific IgE antibodies to bind to the surface of mast cells and basophils. Second, a repeat exposure to the allergen causes those mast cells and basophils to release proinflammatory molecules like histamine, leading to the signs and symptoms of atopic conditions, including asthma and allergic rhinitis.