Biting insects include ants, fleas, flies, no-see-ums (flies called midges), and mosquitoes. Stinging insects include bees, wasps, and hornets. These insects are usually a nuisance, but some people are may have allergic responses to bites or stings. Some insects pass diseases to people.
The group called arthropods that includes insects also includes arachnids—spiders, scorpions, ticks, and mites. The main poisonous spiders in the United States are the brown recluse, black widow, tarantula, and hobo. Most spider bites are uncomfortable but heal without problems.
Local pain or itching occur first, then redness and swelling. Bites can become infected. Stings cause local pain and swelling. Many stings can cause swelling, weakness, confusion, trouble breathing, fainting, vomiting, and diarrhea. Kidney failure, cardiac arrest, and death can occur with severe allergies. Disorders such as Lyme disease are spread by ticks, and encephalitis is spread by mosquitoes.
Brown recluse spider bites can cause stinging, redness, and swelling and blood-filled blisters, ulcers, and infection. Hobo spider bites cause similar problems plus headaches and muscle aches. Black widow spider bites usually cause intense burning, sometimes followed by spasms of the abdomen (belly), limbs, and back, with high blood pressure, sweating, and vomiting. Tarantula bites are like wasp stings with severe pain, redness, and swelling.
Diagnosis is based on a medical history and physical examination. Blood tests are needed for suspected Lyme disease, babesiosis, ehrlichiosis, or Rocky Mountain spotted fever or if fever, rash, headache, or joint pains are present.
It’s best to avoid getting bitten or stung. Use repellents, wear long sleeves and pants and a hat, and put screens in doors and windows. For most bites and stings, ice or cold packs, steroid creams, and antihistamines help itching and swelling. Oral anti-inflammatory steroids are used to treat severe reactions or many bites or stings. Antibiotics are given for tick fevers such as Lyme disease.
Hives or more severe allergic reactions need quick medical care. Some people with severe allergy must use epinephrine self-injectors.
Most spiders try to avoid humans and bite only when trapped. Bites usually heal on their own, but applying cold packs (ice) and elevating the limb if the bite is on a leg or arm will help. A tetanus toxoid injection, pain medicines, and muscle relaxants may be needed. Black widow antivenin is given for very severe cases (trouble breathing) or for pregnant women with black widow bites. Anti-inflammatory steroids and antihistamines may help relieve itching from tarantula bites.
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