Allergic rhinitis is associated with sleep disturbances, daytime somnolence, and fatigue. The exact relationship between rhinitis and sleep disturbance is unknown; however, both the symptoms and underlying pathology of allergic rhinitis can interfere with sleep quality. Nasal congestion, which has been shown to cause sleep-disordered breathing, is thought to be primarily responsible for rhinitis-related sleep disorders. The severity of nasal congestion follows a circadian rhythm, being worst at night and in the early morning. Chronotherapy is the study of the effects of administration time on the safety and efficacy of drug therapy based on circadian influences on the pharmacokinetics and pharmacodynamics of medications. Chronotherapy studies in allergic rhinitis suggest there are benefits to nighttime dosing of antiallergy medications. For example, the antihistamine mequitazine has shown improved efficacy when administered in the evening compared with morning dosing. More study is needed to determine whether this is a class effect. Leukotriene receptor antagonists are indicated for evening administration; these drugs significantly improve nighttime rhinitis symptoms. Intranasal corticosteroids administered in the morning have demonstrated efficacy in improving nighttime symptoms; however, it is unknown whether evening administration would improve their effects on nocturnal rhinitis symptoms. Because of the significant detrimental effects of nocturnal rhinitis symptoms on quality of life, allergic rhinitis therapies should be evaluated for efficacy in ameliorating nighttime symptoms.