Identifying the culprit allergen in seasonal allergic rhinitis

Seasonal allergic rhinitis (SAR) is the main form of rhinitis in children whereas in adults it accounts for about a third of cases of rhinitis. It is a risk factor for the development of asthma and chronic rhinosinusitis. The most common allergic triggers are grass and tree pollens, allergy to moulds and weeds is less common. Identifying the months of the year when an individual is symptomatic will help define the culprit allergen. If there is a clear recurring seasonal history the diagnosis may be made on the strength of the history. Skin prick tests are available in specialist clinics and are a useful tool in differentiating SAR from non-allergic rhinitis and defining the culprit allergen(s). Specific IgE tests for suspected allergens can be performed if skin tests are not available. A positive specific IgE test to an allergen does not necessarily mean that clinical allergy is present, it may reflect sensitisation of the immune system. Although, in general, specific IgE tests have a high negative predictive value they are less sensitive than skin prick tests for grass pollen and moulds. Allergen avoidance is the first step in the management of any allergic rhinitis. Oral non-sedating antihistamines are recommended as first-line treatment for mild SAR, higher doses may be necessary in moderate to severe SAR. Intranasal corticosteroids should be used in moderate to severe forms of SAR and also in mild forms where treatment with antihistamines has failed. There are no major differences in terms of efficacy between different corticosteroid preparations. Long-term growth studies in children using fluticasone, mometasone and budesonide (but not beclometasone) have been reassuring.