Sudden onset of urticaria is mostly caused by allergic factors, such as food or inhalant allergies, and infection can also induce urticaria, and most of the urticaria induced by infection is accompanied by fever. If the patient suddenly appears erythematous, windy, with obvious itching, clinically judged to be urticaria, you can immediately take oral anti-allergy drugs, commonly used is the second generation of H1 receptor antagonists, such as loratadine or cetirizine, with antihistamine, inhibition of mast cell degranulation, anti-allergic, anti-itch and other effects, more itchy patients can also be applied topical stove glycol lotion. Patients with more severe urticaria can also develop anaphylaxis, such as dizziness, head confusion, shortness of breath, and other manifestations. After taking anti-allergy medication temporarily, if the symptoms do not ease, patients should actively seek medical attention and may require treatment with hormones or epinephrine, etc.