The circadian clock functions as a potent regulator of allergic reaction.

Symptoms and laboratory parameters of allergic diseases exhibit prominent ~24-h variations. For instance, in most allergic rhinitis patients, symptoms worsen overnight or early in the morning. Accordingly, there are benefits to nighttime dosing of anti-allergy medications in such patients. Although the circadian pathophysiology of allergic diseases is well documented, the biological basis of this phenomenon remains poorly understood. Recent studies have begun to reveal that the internal timekeeping system termed the circadian clock plays a key role in temporal regulation of allergic reaction, and may therefore underlie the circadian pathophysiology of allergic diseases. Here, we review new knowledge that highlights the emerging role of the circadian clock as a potent regulator of allergic reactions. Given the strong influence of circadian rhythms on allergic diseases, we believe that research on how the time of day impacts allergic reaction which we may call 'chronoallergology' will provide new insight into previously unknown aspects of the biology of allergies. Such knowledge should facilitate novel strategies for prevention and treatment of these diseases.