Allergy method), and provocative and neutralization (subcutaneous) testing or sublingual provocation. Before a diagnosis of allergic disease can be confirmed, other possible causes of the presenting symptoms should be considered. Vasomotor rhinitis, for example, is one of many illnesses that share symptoms with allergic rhinitis, underscoring the need for professional differential diagnosis. Once a diagnosis of asthma, rhinitis, anaphylaxis, or other allergic disease has been made, there are several methods for discovering the causative agent of that allergy. Dietary avoidance is not effective as a preventative measure for allergies. Early exposure to potential allergens may actually be protective. Fish oil supplementation
Allergic rhinitis of prolonged steroid therapy. Other measures that may be used second line include: decongestants, cromolyn, leukotriene receptor antagonists, and nonpharmacologic therapies such as nasal irrigation. Topical decongestants may also be helpful in reducing symptoms such as nasal congestion, but should not be used for long periods, as stopping them after protracted use can lead to a rebound nasal congestion called rhinitis medicamentosa. For nocturnal symptoms, intranasal corticosteroids can be combined with nightly oxymetazoline, an adrenergic alpha-agonist, or an antihistamine nasal spray without risk of rhinitis medicamentosa. Nasal saline irrigation (a practice where salt water is poured into the nostrils), may