The reason why pediatric urticaria flares up at night may be due to a decrease in the efficacy of the medication, or due to an allergic reaction or a decrease in the secretion of adrenocorticotropic hormone. 1. Decrease in drug efficacy: At night, due to the longer time, the drug is gradually metabolized during the night, the efficacy of the drug will decrease, which will lead to the recurrence of urticaria. 2. Allergic reaction: urticaria may be caused by contact with allergic substances, if parents do not pay attention to bedding hygiene, resulting in the presence of more mites in the duvet cover, bed sheets, at night when the child sleeps, when contacted with allergens, it is easy to induce urticaria attacks. 3. Reduced secretion of adrenocorticotropic hormone: As adrenocorticotropic hormone has the effect of inhibiting allergic reactions, and adrenocorticotropic hormone is secreted more during the daytime, and the secretion of adrenocorticotropic hormone is relatively reduced at night, due to the reduction of the secretion of adrenocorticotropic hormone, leading to the reduction of the ability to inhibit allergic reactions, which may lead to the attack of urticaria. Pediatric urticaria should be timely medical treatment, and actively cooperate with the doctor for treatment and conditioning, to prevent recurrence of urticaria.