Allergic Rhinitis

Allergic Rhinitis

Jim Ellsmere, B.Eng, Meds '99 Dalhousie University

Reviewed by E. Massoud MD FRCCS, Assistant Professor, Dept. of Otolaryngology, Dalhousie University

What is allergic rhinitis?

Allergic rhinitis is an inflammation of the nasal mucosa which is triggered by an allergic reaction. The inflammation is caused by an excessive degranulation of mast cells. Increased IgE levels to certain allergens are thought to be responsible for this phenomenon. When exposed to these allergens, the IgE covered mast cells degranulate releasing inflammatory mediators and cytokines which results in a local inflammatory reaction.

Epidemiology

Over the last couple of decades, there appears to have been an increase in the prevalence of allergic rhinitis. This increase is partially attributable to the limited ventilation in most modern housing. Some have also suggested pollution may have a role. Recent studies however suggest this is probably not the case. In one study comparing the rates of allergic rhinitis in two German cites, no significant difference was found despite the significantly higher levels of pollution in the eastern city.

Inciting Factors

The triggers responsible for allergic rhinitis may be classified as either seasonal or perennial. Seasonal allergens are for the most part found outdoors. Common seasonal allergens include tree, grass and weed pollens, and airborne molds. As one would suspect, these allergens depend very much on the geographic area. Perennial allergens tend to be found indoors and include among others things, dust mites and animal dander (especially from cats).

Signs and Symptoms

People suffering from allergic rhinitis usually complain of itchy eyes, nose and palate, watery rhinorrhea, nasal obstruction, sneezing attacks that are often violent and prolonged, conjunctival irritation and lacrimation. They often have edematous nasal mucosa which is classically pale or violet in colour (see Figure) and excessive clear mucus within the nose which often contains large numbers of eosinophils. Children may have a nasal skin crease as a result of chronically trying open their nasal airway, the "allergic salute".

Investigations

The most important part of the physician's workup is taking a thorough history. A temporal relationship between allergen exposure and symptoms is almost diagnostic. The person who suffers all week but is fine on the weekend is very likely allergic to something at work. Skin testing is valuable to help pinpoint possible allergens but is never absolutely definitive. It should not be used to do screening without a clinical suspicion because of its high rate of false positives. In vitro tests for allergen-specific IgE are indicated for those patients with contact dermatitis or a questionable false skin test. A high serum IgE level can also provide some information but, in general, it is not sought because it is very non-specific.

Management

The first step in managing a patient with allergic rhinitis is to educate them about the importance of avoiding allergen contact. Even the best medical therapies are ineffective in the face of a high allergen load.

Antihistamines are very effective in acute episodes. Generally, the non-sedative antihistamines are preferred to sedative ones. However, if for financial reasons the non-sedative antihistamines are not an option the patient should be instructed to take their antihistamines before bed.

Topical vasoconstrictors (see Nasal Sprays) may be added to the antihistamines for temporary relief but their use should be limited to less than 5 days to minimize the risk of developing rebound nasal congestion.

For patients with moderate disease, sodium cromoglycate may be taken prophylactically. However, this might not be popular with patients because it requires them to take medications four times a day.

When antihistamines and decongestants are insufficient or patients require daily medications, topical steroids should be considered. In general, they are very effective. Patients starting topical steroids should be taught that it takes three or four days before they will see any beneficial effects.
For severe cases, desensitization therapy has also been shown to be effective.
Surgery has a role for patients who have either septal deviations or large turbinates and chronic rhinitis.

Not all rhinitis is allergic! Check the Differential Diagnosis of Rhinitis for other ideas.

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