Insect Bites or stings Mosquitoes, ticks, bees, wasps, spiders, ants, chiggers, and other insects can leave behind itchy, painful, or swollen skin reactions. Most bites and stings improve with simple home care, but some can cause infection, allergic reactions, or illness that needs prompt medical attention. What is an insect bite or sting? An insect bite occurs when an insect feeds or irritates the skin, often causing itching, redness, and a small bump. A sting occurs when an