Jan Bloom often walked her dog in the thick trees and grass behind her apartment in Tennessee. One morning Bloom woke up nauseated. Her entire body ached and there was a hot, painful swelling on her back.

When her doctor discovered a tick lodged there, he suspected that Ehrlichiosis — a tick-borne bacterial infection — was the cause of the illness and swelling. Tests confirmed the diagnosis and Bloom began a course of strong antibiotics.

The swollen area blew up to the size of a grapefruit and took two weeks to subside. During this time, Bloom was confined to bed and extremely sick.

“It’s hard to believe that one bite could cause so much trouble,” she says.

Biting bugs among us

A bug bite can be as harmless as a tiny nip by an ant or as dangerous as a chomp from a brown recluse spider.

But how can you know what bit you? Read on to learn clues to identifying some common insect bites and how to deal with them.

Mystery bite #1

black widow spiderWhat it’s like: A pinprick pain followed by the appearance of one or two tiny dots (fang marks), slight swelling and redness.

Symptoms: Between 30 and 60 minutes after the bite, muscle cramps and spasms, chills, fever, nausea, vomiting, sweating, shock, high blood pressure and severe pain in your belly, chest or back.

What you were doing when bitten: Were you near a woodpile, swimming pool or rooting through boxes or drawers?

What it may be: A black widow spider bite. Black widows, distinguishable by a red, orange or yellow hourglass on their bellies, hide in dark places like drawers and woodpiles. They spin extremely sticky webs and are common in the southern and western regions of the United States.

What to do: Seek medical treatment immediately. You may need an antivenin and/or a tetanus booster. The bite likely will improve in two to three days, although some mild symptoms may take weeks to go away.

After calling for help, apply ice and call the National Poison Control Center's number at 1-800-222-1222 for further instructions.

Prevention: Wear long sleeves and pants in areas where black widows may be. Never reach into a dark space without gloves on. (Photo: Sari ONeal/Shutterstock)

Related: Buzz Off! 7 Ways to Avoid a Wasp or Bee Sting

Mystery Bite #2

brown reclusive spiderWhat it’s like: You may feel a sharp sting when you’re bitten or nothing at all. Pain usually sets in within eight hours and becomes increasingly severe. You may see a blue or purple area around the bite surrounded by a white ring and then a red outer ring in a bull’s-eye pattern. A fluid-filled blister also may develop.

Symptoms: Fever, nausea, vomiting, headache, abdominal pain, joint pain, and muscle cramping. You may develop a rash.

What you were doing when bitten: Were you near a woodpile or getting something from a shed, drawer or cabinet?

What it may be: A brown recluse spider bite. The brown recluse has a violin-shaped mark on its back that isn’t always easy to see. It’s mainly found in the central or southern United States, but has been found in many other areas as well. Brown recluses tend to like dark spaces like woodpiles and sheds. Indoors they’re partial to cupboards and closets.

Symptoms: You may feel fever, nausea, vomiting, headache, abdominal pain, joint pain and muscle cramping. You also may develop a rash.

What to do. A brown recluse can cause a serious ulcer at the location of the bite, which may require surgery. In rare cases, the bite can be fatal. Seek emergency medical treatment immediately. The ulcer can take around six weeks to go away, and the bite can leave a large crater and scarring.

Prevention: Wear gloves when reaching into dark areas and long pants and long-sleeved shirts when cleaning. (Photo: Miles Boyer/Shutterstock)

Mystery bite #3

tickWhat it’s like: You aren’t likely to feel anything. You simply may notice a bite that’s red, enlarged, itchy and painful.

What you were doing when bitten: Ask yourself whether you’ve been in tall grass, weeds or in the woods recently.

What it might be: A tick bite. Ticks can bite anywhere, but they tend to move to a warm area before attaching to you — behind an ear, in hair, under an arm or in the groin area.

Symptoms: A flu-like illness, if infected. One tick-borne infection, Lyme disease, may result in a bull’s-eye rash. Rocky Mountain spotted fever, another potentially life-threatening disease carried by ticks, can cause a spotted, splotchy rash on the wrists, ankles, palms and soles of the feet that gradually spreads outward.

What to do: Remove the attached tick immediately and save it to show a doctor. Get tested as soon as possible; you may need treatment with antibiotics.

Prevention: The best way to prevent tick bites is by using an insect repellent and avoiding tick habitats. Also after spending time in the outdoors, check every inch of your skin for the tiny parasites. (Photo: daksel/Shutterstock)

Related: How to Treat Bee Stings and Fire Ant Stings

Mystery bite #4

What it’s like: A sharp, painful bite, followed by two to three small bumps on your feet, ankles or legs, each with a small red dot in the center. They are raised, red and itchy, and they continue for irritate you over the next several weeks.

What you were doing when bitten: Were you been playing with your dog or cat, or visiting a house or basement recently vacated by a family with a dog or cat?

What it might be: A flea bite. Flea bites usually are harmless. The biggest risk is infection from scratching.

Symptoms: Itching. In extremely rare cases, fleas can carry different types of plague, which cause symptoms like swollen lymph nodes, weakness, fever, headache, bleeding under the skin and fast-moving pneumonia.

What to do: See a doctor right if you develop symptoms other than itching. If diagnosed and treated with antibiotics, you should make a full recovery. Otherwise you can us an over-the-counter oral or topical antihistamine.

Prevention: The best way to avoid fleabites is to treat your pets for fleas. If you enter an area you know is infested with fleas, use repellent.

Mystery bite #5

bed bugWhat it’s like: You likely won’t feel anything but you’ll notice rows or clusters of small bites about the size of mosquito bites on your back, legs, trunk or elsewhere. You’re likely to notice them in the morning when you wake up.

Where you were bitten: Have you stayed in a hotel lately?

What it might be: A bedbug bite. Bedbugs are blood-feeding parasites that live usually in the crevices around a mattress, but can move into any tight, hidden spot. Some unlucky travelers bring them home from their vacation.

Symptoms: Itchiness. Bedbugs carry no diseases, so their bite is harmless unless you have an allergic reaction or scratch to the point of infection.

What to do: If you notice clusters of bites and are pretty sure mosquitos aren’t the cause, check for bedbugs. You may need professional help getting rid of them. An oral or topical antihistamine should give relief if it is needed. (Photo: Aureus Virid/Shutterstock)

Related: What’s Hiding In Your Mattress?

Mystery bite #6

What it’s like: Red center surrounded by a blister-like area. You also may see clusters of tiny red dots on your skin. Bites are likely to be on your ankles, armpits, groin and behind your knees, or around the waistband of your pants or cuff of your sock.

Where you were bitten: Have you been sitting on or lying in the grass in the South or Midwest, or walking through the woods there?

Symptoms: Extreme, maddening itchiness. The itching will begin a few hours after you’re bitten and can last up to a few weeks.

What it might be: Red bug (chigger) bites. Red bugs are the larval stage of certain mites that are so small they’re visible only when they’re clustered together. They’re found around lakes, rivers and wooded areas. Red bugs inject an enzyme that destroys skin cells, turning it into their food.

What to do: Red bugs carry no diseases, so the only risk is allergic reaction or infection from scratching. To ease the itch, use calamine, corticosteroids, oral and topical antihistamines.

Prevention: In red bug-infested areas, wear long pants, a shirt with long sleeves and collar and boots. Tuck your pant legs into the boots. Don’t lie down in the grass.

You also may want to try using insect repellent and treating your clothing with a permethrin product. If you know you’ve been in an infested area, shower right away to remove any bugs as quickly as possible.

Related: How to Treat Bug Bites

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Tami Haguel is a freelance writer in Sacramento, California.