Redness, swelling and blisters after mosquito bites are clinically known as insect bite dermatitis, which is caused by an allergic reaction to mosquito bites. Mosquito bites the human body, its salivary glands in the saliva will be injected into the human body, because its saliva contains a variety of anticoagulant substances, resulting in the human body was bitten by the skin parts of the petechiae. Mosquito saliva also contains salivary allergens, adenosine deaminase and other allergic reaction-related proteins, so mosquito bites will make the human body appear local or systemic allergic reactions, manifested as local skin redness, swelling, hard lumps, small blisters, and can be accompanied by varying degrees of itching, burning and other symptoms. If you go to a place with more mosquitoes, it is recommended that you do a good job of mosquito repellent work when you go out and try to wear long clothes and long pants.