When stung by a wasp to reduce swelling, first of all, we should promptly remove the poisonous needle, use a lot of water or soapy water, repeatedly wash the stung area, it is recommended to promptly consult a doctor, under the guidance of the doctor for treatment. First of all, it is clear whether the hornet’s poisonous needle is left in the stung skin, if so it should be removed immediately, and then immediately use a lot of water or soapy water to wash the stung area repeatedly. This is because alkaline soapy water can neutralize acids and provide relief. You can also use glucocorticoid ointment or 3% boric acid solution to stop the itching, swelling and other symptoms. The reason why the stung area is swollen is because the venom of the hornet has an allergic reaction to the human body, you can take some anti-allergic drugs such as loratadine and levocetirizine hydrochloride under the guidance of a doctor. It is recommended to actively seek medical advice and follow the doctor’s instructions to use medication.