Many patients with urticaria have nocturnal flare-ups or exacerbations, which are influenced by a variety of factors such as environmental stimuli and hormonal changes in the body. The onset of hives is characterized by lightness during the day and heaviness at night, and there are many reasons for this phenomenon. First of all, at night, the hormone level in the body will change and the release of mediators that can inhibit allergy will decrease, so the allergic reaction to certain substances may be aggravated. At the same time, the body is less active at night, blood circulation is weakened, the deposition of toxins and impurities in the blood vessels will make the itchy skin and other symptoms intensify. In addition, the external stimulus at night is also greater than during the day. At night, most people will have the habit of resting with the windows closed, resulting in poor indoor air circulation, dust or mites and other allergens can not be timely circulation to the outdoors, increasing the exposure of allergy sufferers. When resting at night, they will also come into contact with mites on pillows and bedding, which will intensify their allergic reactions and cause the erythematous and itchy symptoms of hives. To avoid the aggravation of hives at night, first of all, you should keep the room ventilated, wash the bedding more often and carry out insecticide treatment, and also enhance blood circulation with appropriate activities, and most importantly, take medication in time to avoid recurrence of symptoms. Hives appear at night mainly because the body’s internal protection is weakened and external stimuli are strengthened, hives will appear after contact with allergens and should be treated actively.