Summer is a colorful world where people wear colorful clothes and enjoy the natural beauty, while the insect world is also exceptionally active. Today we are going to learn about one of the most common summer diseases, papular urticaria. Most people don’t know the name of papular urticaria, but its nickname is certainly a household name, and that is “insect bite dermatitis”. Papular urticaria is an allergic reaction caused by the bite of insects such as mosquitoes, bedbugs, lice, fleas, mites, etc. Of course, not everyone has a reaction, and it is related to atopic constitution. Clinical manifestations are related to atopic constitution, insect saliva toxicity, etc.; generally prevalent in children, adults can also occur; lesions are mostly located in exposed areas, such as the extensor side of the limbs, non-exposed also appear; initial lesions appear as clusters or scattered slightly fusiform red papules of mung bean to peanut size, some may have pseudopods, often with small blisters at the top, some appear as large hemispherical elevated tense blisters, content clarified, without surrounding erythema. Old and new lesions often coexist. There is no systemic symptoms. Local lymph nodes are not enlarged. Scratching may cause secondary infection, fever and acute lymphangitis (commonly known as “red line”). The lesions generally fade after 1 to 2 weeks, leaving temporary hyperpigmentation, but new rashes can still appear. Treatment: Topical medication can be used such as glyburide lotion, glucocorticoid preparations, such as the emergence of large blisters, sterile syringes can be used to extract herpes after disinfection with iodine volts, exudate more than the application of 0.1% safranin liquid cold wet compress; oral antihistamines such as (loratadine, cetirizine, levocetirizine, etc.); such as secondary infection can be added with antibacterial agents. Prevention: prevent mosquito bites, go to humid, flowery and forested places as little as possible; try not to keep pets or stay away from them; change and dry clothes and bedding regularly.