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Bad Bugs: Identify Bug Bites From Mosquitos, Spiders and More


Black-legged ticks and deer ticks can transmit Lyme disease to humans.

Ticks are often found in plants and brush, and can attach to and bite people and animals. Most tick bites are not harmful; however, ticks can carry serious diseases including Lyme disease and Rocky Mountain spotted fever.

Tick Bites

Tick burrowing into human skin where they feed on blood.

Most commonly, ticks attach to warm, moist, and hard-to-see parts of the body including the scalp, armpits, groin, skin folds, and other hairy areas. Ticks must be removed properly to minimize the chances of infection

  • Wear appropriate clothing outdoors to reduce exposure
  • Use tick repellant with DEET
  • Check for ticks if you spend time in the woods

Lyme Disease

Bull's-eye rash indicating Lyme disease.

A Lyme disease bacterium is carried in the deer tick (in the northeastern, mid-Atlantic, and north-central U.S.) and the western blacklegged tick on the Pacific Coast. In most cases, the tick must be attached 36-48 hours to spread Lyme disease. A circular, red, expanding rash (erythema migrans, or a “bullseye” rash) is one of the first symptoms of Lyme disease. Other symptoms include fatigue, chills, fever, headache, muscle and joint aches, and swollen lymph nodes. Treatment in the early stages with antibiotics is generally effective.

Poisonous Black Widow Spiders

A female black widow with its distinguishable bright-colored 'hourglass' mark on the underside.

Black widow spiders are about ½ inch wide; with a shiny, black, globular abdomen that has the distinctive red hourglass on the underside. Only the female of the species bites humans. They live throughout the U.S., but most are found in the southern regions.

Black Widow Spider Bites

Close-up tiny red fang marks of a black widow spider bite on finger.

Black widow spider bite symptoms usually start 20 minutes to one hour following the bite, and can include pain, though not all people experience pain. Other symptoms include muscle cramps and spasms, abdominal pain, tremors, weakness, or a rise in blood pressure. Seek medical attention immediately. Treatment includes antivenin (which counteracts the spider toxin) and pain medications if necessary.

Deadly Brown Recluse Spiders

Brown recluse spiders have a 'violin' pattern in the upper body, where legs attach.

Brown recluse spiders are extremely poisonous, and bites can cause infection and illness. They are found mostly in the Midwestern and Southeastern U.S. They are yellowish-tan to dark brown in color with darker legs that are about one inch in length. They have a characteristic violin pattern on their back.

Brown Recluse Spider Bites

A photo of a brown recluse spider bite.

The bite of a brown recluse spider is usually painless, but may feel like a mild bee sting. Symptoms of a brown recluse spider bite include severe pain at the site of the bite that develops about four hours after the bite; followed by severe itching, nausea, vomiting, fever, and muscle pain. See a doctor immediately if you think you have been bitten by a brown recluse spider bite. If possible, bring the spider to the ER for proper identification.

Itchy Head Lice

Head lice (louse) crawling out of hair onto a comb.

Head lice are about 2-3 millimeters (mm) long, and they infest the head and neck area, usually hidden in your hair. Head lice spread through direct contact with the hair of a person infested with head lice. It is most common among preschool and elementary school-aged children, and members of the household of children who are infested with head lice. Head lice are not known for spreading disease, however, they may cause itching, and scratching may lead to infection.

Head Lice Remedies

A photo of a head lice infestation and skin infection of the scalp from scratching.

Treatment is recommended for anyone with an active infestation of head lice. Pediculicides (medicines that kill lice) may be prescribed by your doctor. Wash all clothing and bedding used by the person infested with head lice. Often, it is recommended that family members also be treated at the same time to prevent further head lice infestation.

Fleas: Not for Pets Only

A close up side view of a cat flea.

Fleas are not just a problem for Fido – they can bite people too. Fleas are about 2.5 millimeters (mm) long, they are reddish-brown in color, and while wingless, they can jump large distances. They suck blood from their host to feed.

Flea Bites

Flea bites shown on a leg result in raised itching spots with a puncture in the center.

Some people may develop an allergic reaction to a flea bite. Scratching an itchy flea bite can cause the skin on and around the bitten area to break open, which can lead to infection. Make sure all pets in your home are on flea preventative products, keep your home clean, and treat any flea infestations that may occur.

Bee, Hornet, Wasp, Yellow Jacket

A photo of a yellow jacket wasp that can inflict multiple stings.

The stings of bees, wasps, hornets, and yellow jackets can cause severe reactions in people who are allergic to their stings. Normal reactions include pain, redness, and swelling around the site of the sting.

Bee, Hornet, Wasp, Yellow Jacket Stings

A wasp sting (left) and a severe allergic reaction to a wasp sting (right).

If you are allergic to bees, hornets, wasps, or yellow jackets, seek emergency care immediately to prevent or manage an anaphylactic reaction. Use an EpiPen (epinephrine) if you have one. In all cases, remove the stinger if possible to avoid receiving more venom, and clean the sting area with antiseptic. You may take over-the-counter antihistamines for itching or hives, and over-the-counter nonsteroidal anti-inflammatories (NSAIDs) for pain and inflammation.

Fire Ants

A close up look at a red fire ant.

The red imported fire ant is found mainly in the Southern U.S. They are reddish brown to reddish black and have a stinger. They build large dirt mounds, usually in sunny areas. Their bite usually is painful, and will cause an itchy, raised area on your skin (hive), followed by a pus-filled blister.

Fire Ant Stings

Painful stings from a fire ant that quickly fills with pus.

When a fire ant bites you, you will feel it! An itchy hive will develop. Hours later, a blister filled with pus can form. If you suffer from a severe allergic reaction to a fire ant bite, seek medical care immediately. Otherwise, to help relieve the pain and itching, use over-the-counter pain relievers and antihistamines. Do not break the blisters, and keep the area clean to avoid secondary infection.

Itchy Chiggers

Scanning electron micrograph of chiggers which are less than 1/150th of an inch in diameter.

Chiggers are a type of mite from the family known as Trombiculidae. They are barely visible to the naked eye, and in their juvenile (larval) form, they can bite humans. Chiggers found in the U.S. do not spread disease, but their bites can cause intense itching and small red bumps.

Chigger Bites

Itchy red welts from chigger bites on a man’s leg.

Itching from chigger bites is most intense 1 to 2 days following the bite. This is when the chigger falls off and can leave red welts that may resemble a blister or pimple. Scratching can lead to a secondary infection, so treatment is directed at relief of itching symptoms. Use over-the-counter antihistamine creams to help relieve itching and prevent scratching. Consult your doctor if you have concerns.


Scabies is caused by tiny mites that burrow into your skin.

Scabies are mites that burrow into the skin, causing intense itching. Scabies spread by close contact with a person infested with scabies, or by sharing towels, sheets, and other personal items with a person infested with scabies.

Treating Scabies

Scabies mite infestation showing resulting in a rash and sores on the wrist.

It can take weeks after the scabies mites burrow into the skin before you will experience severe itching or rash, with small blisters or sores. The intense itching is usually worse at night. Most commonly, the itching will be between the fingers, on the outside of the elbows or armpits, around the waistline, or on the buttocks. Scabies can only be cured with medicated creams, lotions, or pills. Family members who share a household with a person infested with scabies may also be prescribed treatment.


A photo of a bedbug feeding on human skin.

Bedbugs are reddish brown, and less than 1 millimeter (mm) in size. They are frequently found in bedding, but can also be found in areas of clutter, or in old furniture.

Bedbug Bites

Bedbug bites on person's arm.

Most of the time, the reaction to a bedbug bite is mild, and usually in the form of small, red, itchy bumps. Treatment includes over-the-counter cortisone creams and antihistamines to relieve the itching. Excessive scratching can cause a secondary infection.

Puss Caterpillar

A puss caterpillar or hive-producing caterpillar.

The puss caterpillar (woolly slug, or asp) is the most toxic caterpillar in the U.S., and is found mostly in Southern states. It measures about 1 inch long and appears furry. The longer hairs camouflage spines that have venom. It feeds on shade trees such as elm, oak, and sycamore, or bushes such as holly.

Puss Caterpillar Stings

Evidence of hive on skin from contact with a puss caterpillar.

Symptoms of a pus caterpillar bite include immediate waves of intense pain, itchy rash, nausea and vomiting, restlessness, fever, muscle cramps, and symptoms of shock. If you come into contact with a puss caterpillar, remove the broken-off spines by using cellophane tape or a commercial facial peel, and call your doctor. Apply an ice pack and take over-the-counter antihistamines to relieve itching.

Deadly Scorpions

A photo of the Arizona bark scorpion whose venom is very dangerous.

Scorpions are related to spiders and mites, and are found mostly in the Southern and Western U.S. They range in length from about 9 to 21 cm, and the last tail segment contains the stinger that transmits a toxin to the recipient of a sting. Most scorpions are harmless, but some can be lethal. Scorpion sting symptoms include pain, swelling, and itching at the sting site. Severe symptoms include numbness, difficulty swallowing, blurred vision, seizures, and difficulty breathing. Seek medical attention immediately if bitten by a scorpion.

Painful Deerflies

A close up of a deerfly biting into human skin.

Deer flies are about the same size as houseflies, and they are yellow or black in color, with patterned wings. They are mostly active on warm, sunny days with little wind and they thrive in areas such as beaches, lakes, or woods near damp areas. Bites are usually painful, though most of the time not severe. In rare cases, the flies can transmit the Tularemia bacterium, which requires medical attention. Prevent deerfly bites by wearing protective clothing and using insect repellent.

Annoying Mosquitoes

A close-up of mosquito feeding on human skin.

For the most part, mosquitoes cause itchy hives when they bite. But they can also carry diseases such as West Nile virus, dengue fever virus, malaria, and others. Scratching mosquito bites can also cause infection. Prevent mosquitoes in your yard by draining standing water. Keep them out of your home by using window screens. To protect yourself, always use insect repellent when outdoors, wear protective clothing, and avoid being outdoors during peak mosquito hours of dawn and dusk.

1st Case of Locally Acquired Chikungunya Virus Reported in U.S.

A carrier of the Chikungunya virus, shown here is an Aedes mosquito biting a hand.

HealthDay news article on MedicineNet

"The first case of locally acquired chikungunya virus, which is transmitted by the bite of a mosquito, has been reported in the United States, federal health officials said Thursday. The case involved an unidentified man from Florida. Until now, all previously reported infections..." Read full article on MedicineNet


A close up of a housefly or domestic fly (Musca domestica) which can carry harmful bacteria.

The housefly is a nuisance pest that can spread diseases such as food poisoning and dysentery. They are gray-colored and about 1/4-inch long. They are attracted to trash, manure, carrion, and moist areas, and can spread bacteria from those areas to parts of your home. Proper sanitation is essential to manage houseflies. Keep trash and food in sealed containers.


A photo of a cockroach, which can trigger asthma and allergic reactions.

Cockroaches can be found all over the world. They not only carry diseases such as salmonella, they can cause allergic reactions. Symptoms of allergy to cockroaches can include itchy skin, scratchy throat, itchy eyes and nose, and even asthma. Prevent cockroach infestation and manage allergic reactions by keeping your home clean and in good repair, and keeping trash covered. Use pest control if needed.

Reviewed by John A. Daller, MD on 6/21/2016

Bad Bugs: Identify Bug Bites From Mosquitos, Spiders and More

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