The burden of allergic diseases

Allergic Rhinitis

Key statements 

• Allergic rhinitis (AR) results from an IgE-mediated inflammation of the nasal mucosa. 

• The disease currently affects between 10% and 30 % of the population. 

• Studies indicate that prevalence rates are increasing worldwide. 

• The classification proposed in the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines is useful for the implementation of treatment. 

• AR is a risk factor for asthma. 

• Other co-morbidities of AR include: sinusitis, nasal polyposis, conjunctivitis, otitis media with effusion, upper respiratory infections, breathing through the mouth, and sleep disorders. 

• AR has a significant impact on patients based on the degree of the severity of their symptoms. It has psychological effects, interferes with social interactions, and creates an economic burden not only for the affected subject, but for the family and for the society at large. 

• Management is based on patient education, environmental control measures, pharmacotherapy and specific immunotherapy

Introduction

Allergic rhinitis is defined by the presence of nasal congestion, anterior and posterior rhinorrhea, sneezing, and nasal itching secondary to IgE-mediated inflammation of the nasal mucosa. It must be differentiated from other non allergic forms of rhinitis with a similar clinical picture

Risk factors for the development of AR include a family history of atopic diseases, increased total serum IgE before 6 years of age, higher socio-economic class, and the presence of positive immediate-type hypersensitivity skin tests. The most common causative allergens include pollens, dust mites, molds, and insects.

Atopic subjects inherit a predisposition to produce specific IgE antibodies that bind to high-affinity receptors on mast cells. In the nose, IgE-bound mast cells recognize the allergen and degranulate, releasing preformed mediators (histamine, tryptase, chymase, kininogenase, heparin, and other enzymes). Newly formed mediators including prostaglandin D2 and cysteinyl leukotrienes are released by mast cells, eosinophils, basophils, and macrophages and produce edema, rhinorrhea, mucosal hypertrophy, mucus secretion, and vasodilation leading to nasal obstruction. Stimulation of sensory nerves results in nasal itch, sneezing, and increased congestion. This early allergic response is followed by a late-phase response starting 4 - 8 hours after allergen exposure, which is characterized by congestion, postnasal mucous discharge, hyposmia, and nasal hyperreactivity to non specific environmental stimuli. Repeated mucosal exposure to allergens results in a priming mechanism by which the amount of allergen required to induce an immediate response decreases as a consequence of the influx of inflammatory cells

Prevalence

Allergic rhinitis is the most common form of non-infectious rhinitis, affecting between 10% and 30% of all adults and as many as 40% of children. Epidemiologic studies show that the prevalence of AR continues to increase worldwide. The World Health Organization has estimated that 400 million people in the world suffer from AR, and 300 million from asthma.

In the United States of America, the prevalence of AR ranges from 3% to 19%. According to the Centers for Disease Control and Prevention, 23.7 million cases were reported in 1996. Overall, it affects 30 to 60 million individuals annually. In childhood, affected boys outnumber girls, but the sex ratio is about equal in adults. AR develops before the age of 20 years in 80% of cases. Increased prevalence is observed in non whites, in some polluted urban areas, and in first-born children. AR accounts for 16.7 million physician office visits annually.

In Europe, the European Community Respiratory Health Survey established the prevalence of AR as being from 4% to 32%. The International Study on Asthma and Allergies in Childhood (ISAAC) reported the prevalence of allergic rhinitis in Latin America.