Most spiders are harmless to people. But there are two spiders in the United States that can cause harm: the black widow and the brown recluse. People bitten by a black widow or brown recluse spider should get medical care right away.
Brown recluse spiders may be light or dark brown. They are ¼ inch to ¾ inch long, and have long, thin legs. Some have a fiddle-shaped mark on their back. They are most often found in the South, West, and Midwest. They live in dark, quiet places such as closets, attics, basements, porches, barns, and woodpiles.
A brown recluse spider bite may be painless at first. Or it may burn slightly like a bee sting. A small, red mark may form at the site. Then small blisters may appear. In 2 to 8 hours, the area may become painful, swollen, and itchy. Other symptoms can include a general feeling of discomfort, fever, joint pain, nausea, and vomiting. In most cases, the bite heals on its own in a week. But in some cases, the skin at the bite site may break down. For instance, the skin may turn black and sink down as the tissue below dies. This can cause an open wound called an ulcer to form. It may take a few weeks to a few months to heal. In rare cases, a brown recluse spider bite leads to more serious problems. These can include muscle damage, kidney failure, problems with blood clotting, and coma.
The bite site will be cleaned. You may get pain medicines and antibiotics. You may get a tetanus shot. If an ulcer forms and causes severe damage to the skin, you may need skin grafting. But most bites heal without scarring.