Chapter 67

#### High Yield Facts

• Allergy related disease is extremely common and will present frequently to the emergency department (ED).

• The diagnosis of allergic conjunctivitis/rhinitis is often missed or delayed.

• Complications of allergic conjunctivitis/rhinitis include exacerbation of asthma, sinusitis, middle ear infections and effusions, and sleep disturbances.

#### Background

Allergic disease is extremely common in the United States and presents frequently to the ED. Forty percent of children will be affected at some point during childhood.1 Pediatric allergic disease is more common in developed countries and the incidence has been shown to be rising dramatically.2,3 Pediatric allergic disease comprises a spectrum of disorders, with the most common being asthma (see Chapter 34), urticaria, allergic rhinitis (AR), and allergic conjunctivitis (AC). The focus of this chapter will be allergic rhinitis, allergic conjunctivitis, and urticaria.

#### Pathophysiology

In general, allergic reactions are due to heightened responses of the immune system to antigens encountered in everyday life. The most severe of these reactions is anaphylaxis, which involves multiple organ systems (see Chapter 68). Allergens are antigens that trigger the allergic response and are most commonly proteins, although carbohydrates and drugs can also serve as allergens. Allergens stimulate production of specific IgE antibodies in the sensitive individual and bind to the surface of the mast cell which usually reside near mucosal surfaces, in submucosal surfaces near venules, and in cutaneous tissue.4 The allergic reaction is triggered when specific IgE antibodies are bridged by the offending allergen which causes degranulation of the mast cell and releases histamine, prostaglandins, leukotrienes, and other inflammatory mediators (Fig. 67-1).4 At the tissue level, this results in increased capillary permeability, vasodilatation, mucosal edema, mucus secretion, and sensory nerve stimulation.4

###### FIGURE 67-1

Release of histamine, cytokines, prostaglandins, and other inflammatory mediators.

#### Allergic Rhinitis

AR affects up to 40% of children in the United States, making it the most common chronic disease in children.5 Because it is so common, the economic burden of this seemingly benign disease is quite staggering.6,7 AR is an IgE mediated disease, but there is also a late phase reaction with tissue eosinophilia, resulting predominantly in nasal congestion.8 AR is frequently associated with other conditions, most commonly allergic conjunctivitis, sinusitis, asthma, and otitis media.9 Children with moderate-to-severe AR may suffer from sleep disturbance and significant impairment of daily activities and performance in school.9 Asthma and AR are closely linked as well, particularly in atopic individuals.8 Treatment of AR has been shown to reduce bronchospasm, ED visits for asthma, and hospitalization.8

#### Diagnosis

The diagnosis of AR in the ED is chiefly clinical, with the main symptoms being nasal congestion or blockage, watery ...

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