A mosquito bite appears as an itchy, round red or pink skin bump.[1] It’s usually a harmless bug bite but can sometimes cause a serious illness, such as the Zika virus (particularly harmful in pregnant women),[2] West Nile virus, malaria, or eastern equine encephalitis (EEE).[1]
For most people, Zika causes a brief, flu-like illness. But newborns of pregnant women with Zika infection have a high rate of microcephaly and congenital anomalies.[2]
For 2024, doctors reported a total of 24 cases of the West Nile virus across 14 U.S. states, according to the Centers for Disease Control and Prevention (CDC).[3] Symptoms an include headaches, body aches, fever, vomiting, joint pain, diarrhea, and a skin rash.[4] People with a more severe West Nile infection may develop meningitis or encephalitis and have symptoms including neck stiffness, severe headache, disorientation, high fever, and convulsions.
The bite of a parasite-infected mosquito can cause malaria, a rare occurrence in the United States, with only about 2,000 cases diagnosed in the country each year, according to CDC data.[5] Symptoms are similar to the flu and can include fever, headache, muscle aches, diarrhea, nausea, and vomiting.
Cases of EEE are rare but deadly. For people with EEE infection, 30 percent do not survive, and many who do develop brain and nervous system problems.[6] Symptoms include headache, fever, vomiting, seizures, diarrhea, drowsiness, and behavior changes.[6] An average of 11 people per year in the United States acquire this virus.[7]
Mystery bites, be gone. Here's our list of the six best mosquito repellents on the market.

2
Bedbug Bites
a person with bedbug bites on their back
Joel Carillet/iStock
You probably won’t feel pain when a bedbug bites, but you may see three or more clustered red marks, often forming a line.[8] They might show up to 14 days after a bite occurs, as bed bugs inject a substance in their saliva that makes bites harder to spot.[9]
Some people develop a mild or severe allergic reaction. This can result in a raised, red skin bump, blister, or a welt known as hives that’s intensely itchy and inflamed for several days.[10]
If you have hives, a lot of bites, or notice a bite that looks infected, you should visit a board-certified dermatologist for treatment, according to the American Academy of Dermatology Association.[8] Bedbug bites can occur anywhere on your body but typically show up on uncovered areas, such as your neck, face, arms, and hands.[8] Although they’re common and irritating, bedbugs do not carry disease, per the CDC.[11]
3
Black Widow Bites
a close up of a spider bite
Getty Images
A bite from a venomous spider, like the black widow or brown recluse, is extremely dangerous and can cause a severe reaction.[12] The black widow’s bite, which shows up as two puncture marks, causes a sharp, immediate pain, with numbness closely following. Other symptoms can last one to three days and include:[13]
An itchy rash
Intense sweating
Breathlessness
Headache
Producing more saliva
Muscle cramps in the shoulders, chest, back, and stomach that hurt
Swollen or drooping eyes
You might not have seen the spider that bit you, but always seek medical attention immediately if there’s a possibility you could have a venomous spider bite. Call 911 or America’s Poison Centers at 800-222-1222. Breathing problems, a growing wound at the site of the bite, intense pain, or spreading streaks or redness are all signs that urgent medical care is necessary.[12]
Most spider bites are not poisonous and cause only minor symptoms like red skin, swelling, and pain at the site — or even no symptoms at all.[12] Other spider bites are a real emergency. If you develop an allergic reaction to a spider bite, with symptoms such as tightness in the chest, breathing problems, swallowing difficulties, or swelling of the face, you need medical care at once.[14] Because tetanus can infect spider bites, the CDC also recommends staying on top of your tetanus booster shots by getting one every 10 years.[15]
4
Brown Recluse Spider Bites
a brown recluse spider bite
Robert D Brozek/Alamy
The brown recluse spider is venomous and usually lives in dark and unused spaces. People often don’t realize they’ve gotten a brown recluse bite until about an hour after the bite.[13] In the hours afterward, the bite may become more painful and look like a bruise or blister with a blue-purple area around it, similar to a bullseye.[13] Later, the bite becomes crusty and develops scarring. This type of spider lives in several Midwestern states, western parts of some Southern states (including Georgia, Kentucky, and Tennessee), and the central Southern states (including Arkansas, Alabama, Louisiana, Mississippi, Missouri, and Texas) and rarely wander outside of these areas, according to the University of Kentucky.[16]
Symptoms of a brown recluse spider bite occur within a few hours and include fever, chills, itching, nausea, and sweating.[17] Some people will have a serious reaction that can lead to kidney failure, seizure, and coma, according to MedlinePlus.[17] Be sure to seek medical attention immediately if you could have been bitten by a poisonous spider. Call 911 or America’s Poison Centers at 800-222-1222.
5
Tick Bites
a tick bite that has turned into a bulls-eye which can signal lyme disease
Thinkstock
Tick bites can be hard to spot and many go without detection. Some cause painful, itchy skin, but many don’t. Ticks often remain on the skin, but they can be so small that they aren’t visible until they grow after feeding on blood. Their bites may cause a skin reaction, like a tiny, hard lump or a rash.[18]
Some tick bites can be dangerous because the insects may carry disease. Black-legged ticks, formerly known as deer ticks, may carry Lyme disease, and dog ticks can spread Rocky Mountain spotted fever (RMSF). Doctors reports up to 30,000 cases of Lyme disease each year in the United States.[19] These infections can lead to various symptoms that show on the skin.
Symptoms of Lyme disease sometimes include a skin rash in the pattern of rings, much like a bull’s-eye on a target, that appears up to a month after the tick bite.[20] Many tickborne diseases also cause fever, fatigue, headaches, muscle and joint aches, chills, and irritation.[18] Later symptoms such as swollen or painful joints, memory loss, or other autoimmune responses that mimic other diseases may present themselves when Lyme disease is in its advanced stages. 
Rocky Mountain spotted fever from a tick bite is rare.[21] It causes a fever, a headache, muscle aches, an upset stomach, and a skin rash.[22] The rash of pinpoint red spots begins on the ankles and wrists after two to four days of fever, but later the rash spreads to the rest of the body. However, 1 in 10 people with RMSF never get a rash, and less than half of those with RMSF get a rash in the first three days.[22] Although this infection can be severe — and even fatal — it is preventable and treatable with prompt medical care using an antibiotic called doxycycline, according to the CDC.[23]
6
Flea Bites
a person with flea bites on their legs
Joe Fox/Alamy
Symptoms of flea bites may begin within hours after you’re bitten, and the bites tend to appear in groups of three or four, either in clusters or a straight line. You may notice itching and swelling around an injury or sore, or a rash of small, red bumps that may or may not bleed. The bite might also have an off-color ring around it.[24]
Flea bites are most common on your ankles and legs, but may also appear in areas above the knee in people who spend a lot of time lying down. If a person has an allergy to flea bites, blisters may form.[25]
If you have a pet, they’re scratching a lot, and you find fleas on them, along with noticing these characteristics in the bites, then it’s very likely that you have flea bites.[24]
Scratching the rash can lead to a skin infection, according to MedlinePlus, and may need medical attention.[25] Per the Cleveland Clinic, antihistamines, hydrocortisone, ice, and natural options such as aloe, chamomile tea, oatmeal, and honey can reduce the itching.[24]
7
Bee Stings
a person with a bee sting on their foot which has caused swelling
iStock
Bee stings cause a sharp pain that may continue for a few minutes.[26] This pain usually resolves in a few hours, but the area may still feel sore to the touch a few days later.[26] A red skin bump and swelling may appear around the site of the sting.[26] Some people have a moderate reaction that sees swelling increase over the next few days. Redness may also be much more severe in people with moderate rather than mild symptoms.[26]
Bee venom inserts proteins that attack skin cells and trigger an immune response, resulting in swelling where the sting occurred or in an entire area of your body, including your throat and lungs.[26] If you have this type of allergic response, called anaphylaxis, it is a medical emergency that needs treatment immediately.[26] Symptoms of a severe allergy to a bee sting include:[26]
Hives
Flushed, pale skin
Itching
Swelling of the tongue and through
Breathlessness
Dizziness
Cramps
Nausea
Vomiting
Diarrhea
Cardiac arrest
Having had a bee sting before increases the chance of anaphylaxis by 25 to 65 percent during the next bee sting, so preventive measures may be necessary, according to Mayo Clinic.[26]
8
Lice Bites
a woman with lice bites on the back of their neck
Alamy
Lice bites are tiny red bumps on the shoulders, neck, scalp, and other areas from small parasitic insects called head lice, body lice, or pubic lice that can live on your clothes or in your bedding.[27] Because lice bites are so small, they usually don’t hurt, but they do itch. The first time a person has lice, the itching may not start for four to six weeks.[27] Some people may develop a large, uncomfortable skin rash from lice bites, especially if they scratch and infection develops. 
Body lice often bite the shoulders, abdomen, and buttocks; head lice bite the head, neck, and shoulders; and pubic lice are a different species that whose bites cause blue-gray spots to develop under the buttocks, chest, and thighs.[28] People with pubic lice may notice lymph node swelling, and if pubic lice have moved to the eyelashes, they might also be aware of irritation, burning, and itching in the eyes.
9
Ant Bites and Stings
a person with ant bites on their arm
Scott Camazine/Getty Images
Ant bites and stings are typically painful and cause red skin bumps. 

Some types of ants, like fire ants, are venomous, and their bites can cause severe pain and a red spot — these are hives that stay in the same area and the most common reaction.[29] A few hours after this, white, fluid-filled pustules or blisters develop and last for several days to a few weeks. These bites tend to appear in groups if they occur under clothing.[29]
Ant bites may also lead to hives, itching, and redness that can develop far from the bite, along with digestive issues such as nausea, belly cramps, and diarrhea.[29] The American Academy of Allergy, Asthma, and Immunology advises that leaving the blisters alone mean they will heal faster, as fire ant venom kills bacteria, so the bite is sterile.[30]
10
Mite and Chigger Bites
a person with mite and chigger bites on their arm
Michael Weber/Alamy
Mites do not usually spread disease, but their bites can irritate the skin and cause intense itching and pain.[31] Itch mites usually feed on insects but will bite other animals, including people. The bites are usually undetectable until itchy, red marks develop that may look like a skin rash.
Chiggers are a form of mite that inject their saliva so that they can liquefy and eat skin, normally on the ankles, behind the knees, and on the ankles, waist, or groin — especially in areas that clothing closely meets skin, like the sock line or bra lines.[32] It’s not technically a bite, as they use their claws to dig in the skin, according to the Nebraska Forest Service.[33] In response to a chigger “bite,” the skin around the bite hardens.[33] The surrounding skin becomes irritated and inflamed (pictured), and an itchy red welt develops that leads to one to two days of severe itching that may last up to a week.[33]
Itch mites also cause a condition called scabies, which is contagious from person to person even if symptoms are not showing, notes the CDC.[34] Female scabies mites burrow into the skin to lay eggs. When the eggs hatch, the larvae come to the skin’s surface. They begin to molt and then burrow back into the skin to feed.[34] This results in a skin rash that may look like acne pimples and create intense itching that gets worse at night.[34] You may also notice light, thin lines on the skin where the mites have burrowed, including between the fingers, in the bends at the wrists and knees, and on the wrists and fingers.
11
Kissing Bug Bites
a close up of a kissing bug
Daniel Heuclin/Getty Images
Kissing bugs, also known as assassin bugs, can pass on the parasites that cause Chagas disease, Trypanosoma cruzi. Around 55 percent of kissing bugs than half of these insects carry Trypanosoma cruzi, per Texas A&M University.[35] In the United States, Chagas disease has developed in about 280,000 people a year, according to the CDC.[36] Many of these do not realize they have it.
Kissing bugs hide in the daytime but emerge at night, often leaving bites on the face and causing a swollen eyelid, known as Romaña’s sign.[36]
In the first few weeks after infection, symptoms of Chagas disease can include fever, fatigue, body aches, headache, rash, a loss of appetite, diarrhea, and vomiting, or it can be symptomless.[36] However, the CDC notes that in the long term, and even decades later, about 20 to 30 percent of people who get a Trypanosoma cruzi infection from a kissing bug will develop serious complications of Chagas disease, including:[36]
An enlarged heart
Heart failure
Abnormal heart rhythm
Cardiac arrest
An enlarged colon, also known as megacolon, which can cause issues with eating and passing waste
12
Hornet and Wasp Stings
what-bit-me-spot-these-bug-bites-hornet-sting-RM-722x406
Kari Marttila/Alamy
Hornets and wasps belong to a family of insects called Vespidae.[37] Their bites are usually painful, swollen, and itchy immediately afterward without causing long-term effects. A person may notice bleeding or redness at the site of the sting.[37]
Many people can simply ice the area to soothe pain, remove the stinger if it has stayed in the skin, and take an over-the-counter antihistamine like diphenhydramine (Benadryl) to help with itching. “After a half hour, you can go on with your business,” says Howard Russell, an insect and arthropod diagnostician at Michigan State University in East Lansing.[37] Symptoms typically disappear after a day or two, says Mayo Clinic.[38]
However, if you’re allergic to bee, wasp, or hornet stings — or you’ve experienced multiple stings — a sting can cause severe allergic reactions, including nausea, rapid heartbeat, swelling, dizziness, hives, and shortness of breath, warns Mayo Clinic.[38] Call 911, and seek emergency medical treatment if you experience any of these symptoms.
Hornets typically build their large paper nests in tree hollows, as well as undisturbed spots in barns, attics, and even walls, according to the University of Kentucky.[39] Hornets will defend their nests (and may attack you) if you get too close, so leave the area if you come across one. If you come across a solitary hornet, leave it alone; hornets typically only sting when threatened, the University of Kentucky notes. And if you do get stung, leave the area right away to avoid another attack, Russell says.
13
Certain Kinds of Flies Can Bite, Too
horse flies and deer flies Black flies buffalo gnats no-see-ums
John Devlin/Alamy
Although horse flies and deer flies most affect the animals in those names, unfortunately being a human doesn’t earn you a free pass. According to the University of Kentucky, these flies can target humans who are outside, and the intensity of their attack varies from year to year.[40] Bites can be extremely painful and cause bleeding, swelling, irritation, or an allergic reaction.[40] Swelling and irritation should disappear in a day or two.[40]
The National Pest Management Association suggests wearing light-colored clothing and insect repellent as the most important strategies for prevention.[41]
Black flies (sometimes called buffalo gnats or “no-see-ums”) are also common throughout the United States and can bite (though they’re not known to spread disease), according to Spokane Regional Health District.[42] They’re small and usually bite around the head, particularly the eyes, ears, and scalp. Their bites can cause swelling, soreness, and numbness that can last for several days.
For all of these types of fly bites, they usually show up as painful, sensitive, raised red bumps, according to the U.K.’s Natural History Museum.[43] These may swell and form blisters if an infection develops.
How to Prevent Bug Bites
The CDC suggests the following to reduce the risk of bug bites:[44]
Reduce activities that increase exposure to insect bites, such as camping, hiking, or interactions with wild animals. Where this isn’t possible, take precautions as necessary.
Understand the particular insects that thrive in locations you’re visiting or nearby. Not all insects pose a risk everywhere in the country.
Use an insect repellent that the manufacturers have registered with the U.S. Environmental Protection Agency (EPA). (The EPA has published an online tool to help you determine which one is appropriate in many varying conditions.)
Use permethrin on clothes and outdoor equipment.
Sleep beneath a mosquito net if a mosquito screen is not present in your room.
When traveling, find out what shots or you may need and any precautions you can take.
Wear clothing that covers the skin.
Shower after spending time outdoors to reduce the risk of tickborne diseases.
Be sure to report any symptoms like fever to a doctor if you’ve spent time outdoors or abroad. They may be able to help you identify diseases from bug bites and begin treatment as soon as possible.