A skin swelling or itch caused by an insect bite or sting, typically from mosquitoes, midges, etc.
昨夜、庭で虫刺されに気づいた。
I noticed insect bites in the garden last night.
虫刺されの痒みを抑える薬を塗った。
I applied medicine to relieve the itch from the insect bite.
虫刺されが腫れてきたら受診したほうがいい。
If an insect bite becomes swollen, it's better to see a doctor.