Infected Mosquito Bite Cellulitis

But for as much good as the histamine does, it also causes the itching, redness and swelling that you see after a mosquito bite.

When to See a Doctor for an Infected Bug Bite

Bug bites can be annoying, but most are harmless and you’ll just have a few days of itching. But some bug bites do need treatment, including:

  • bites from a poisonous insect
  • bites that cause a serious condition like Lyme disease
  • bites or stings from an insect to which you’re allergic

Some bug bites can also become infected. If your bite does become infected, you’ll usually need to see a doctor for treatment. However, most infected bug bites can be treated with a course of antibiotics.

Most insect bites will be itchy and red for a few days. But if one gets infected, you might also have:

  • a wide area of redness around the bite
  • swelling around the bite
  • pus
  • increasing pain
  • fever
  • chills
  • feeling of warmth around the bite
  • long red line extending out from the bite
  • sores or abscesses on or around the bite
  • swollen glands (lymph nodes)

Bug bites can often cause a lot of itching. Scratching may make you feel better, but if you break the skin, you can transfer bacteria from your hand into the bite. This can lead to an infection.

The most common infections of bug bites include:


Impetigo is a skin infection. It’s most common in infants and children, but adults can get it too. Impetigo is very contagious.

Impetigo causes red sores around the bite. Eventually, the sores rupture, ooze for a few days, and then form a yellowish crust. The sores may be mildly itchy and sore.

The sores may be mild and contained to one area, or more widespread. More severe impetigo may cause scarring. No matter the severity, impetigo is usually not dangerous and can be treated with antibiotics. However, untreated impetigo can cause cellulitis.


Cellulitis is a bacterial infection of your skin and the surrounding tissue. It’s not contagious.

Symptoms of cellulitis include:

  • redness that spreads from the bite
  • fever
  • swollen lymph nodes
  • chills
  • pus coming from the bite

Cellulitis can usually be treated with antibiotics. Untreated or severe cellulitis can cause sepsis, a life threatening complication of infection.


Lymphangitis is an inflammation of the lymphatic vessels, which connect lymph nodes and move lymph throughout your body. These vessels are part of your immune system.

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Symptoms of lymphangitis include:

  • red, irregular tender streaks that extend out from the bite, which may be warm to the touch
  • enlarged lymph nodes
  • fever
  • headache
  • chills

Lymphangitis can be treated with antibiotics. If it’s not treated, it can lead to other infections, such as:

  • skin abscesses
  • cellulitis
  • blood infection
  • sepsis, which is a life threatening systemic infection

Lyme disease

Lyme disease is an illness caused by a bacteria transmitted through tick bites. In the United States, Lyme disease is most common in the northeast, mid-Atlantic, and north-central states.

  • bull‘s-eye-shaped rash (not everyone who has Lyme disease gets this rash, but it’s characteristic of Lyme disease)
  • fever
  • headache
  • joint pain
  • muscle pain
  • fatigue

Lyme disease is treated with antibiotics. It’s important to diagnose and treat Lyme disease early, so always check for ticks after being outdoors in areas where Lyme disease is common. Untreated illness can cause issues with your joints, heart, and nervous system.

What Happens When a Mosquito Bite Gets Infected?

Infected Mosquito Bite Cellulitis

Stop scratching! That’s good advice if you have a mosquito bite … but sometimes it’s easier said than done. That bite itches, right? And it itches a lot.

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Here’s why you need to leave it alone: That little bite can transform into a much larger problem if you continually claw at it. Family nurse practitioner Allison Folger, CNP, says infections can develop if you don’t leave the bite alone.

“Scratching the bite to the point of bleeding can open the door for a bacterial skin infection,” explains Folger. “This commonly occurs in children whose nails are understandably dirty from playing outside, though it also happens in adults.”

Here’s what to do if you (or someone you know) just couldn’t resist that urge to scratch.

What is a mosquito bite?

So, you’re outside enjoying the twilight when you feel a familiar pinch on your arm. A quick glance down reveals the small, winged, blood-sucking culprit behind the pain. Yep … a mosquito.

Odds are, a hand smack quickly follows — but it’s too late. You’ve been bit.

Mosquitoes feed on blood using a long, needle-like mouthpart that pierces skin. As the insect sucks your blood, it secretes saliva that enters your bloodstream. That saliva might as well be called itch juice.

Your body registers the mosquito saliva as an allergen, notes Folger. In response, your immune system sends histamine to the bite spot to remove the allergen. (Basically, think of histamine as your body’s bouncer tossing out unruly visitors.)

But for as much good as the histamine does, it also causes the itching, redness and swelling that you see after a mosquito bite.

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What is an infected mosquito bite?

Blame for an infected mosquito bite doesn’t rest solely with the insect. Odds are you played a role in escalating the situation from a mild annoyance and irritation into something requiring extra attention.

The infection, called cellulitis, is from bacteria that enters the punctured skin from your hands. Warning signs include:

  • Swelling of the lymph nodes.
  • Wide-spreading redness around the mosquito bite.
  • Red streaking that extends beyond the initial bite.
  • Pus or drainage.
  • Area feels warm to the touch.
  • Chills.
  • Fever (above 100 degrees Fahrenheit or 37.7 degrees Celsius).

“If you or a child has these signs of infection, it is important to see your doctor,” Folger says.

One easy way to tell if the bite is spreading? Take a pen and draw an outline around the mosquito bite and then check on it later, suggests Folger. That’s a fool-proof, objective way to see if the redness is expanding.

If your doctor confirms the infection is cellulitis, you’ll probably be prescribed antibiotics to kill the bacteria. The most common bacteria causing cellulitis are strep (streptococcus) and staph (staphylococcus).

Home treatment for an infected mosquito bite

Welts from an infected mosquito bite can easily grow to the size of a ping pong ball or mandarin orange. If other symptoms aren’t escalating, Folger recommends the following steps to find some relief.

  1. Clean the bite with soap and water.
  2. Apply an over-the-counter hydrocortisone cream to help reduce the swelling and itching. (This can be followed by calamine lotion, which contains a mild topical anesthetic that may ease the discomfort.)
  3. Use ice packs on the area to help bring the inflammation down.
  4. Reapply the topical medication every four hours as needed.

Your healthcare provider may also recommend using an oral antihistamine (such as Benadryl®), as they’re more effective at providing relief than topical creams.

How to prevent mosquito bites

The best way to avoid a mosquito bite infection (aside from not scratching)? Avoid the bite. To keep those pesky mosquitoes at bay, take these precautions.

  • Cover up with clothing. Bare skin is preferred by mosquitoes. The more covered you are, the less area they have to target.
  • Use insect repellent. Look for products that contain the active ingredients DEET or picaridin, which provide the best protection. Make sure to use any repellent as instructed.
  • Go inside at peak biting hours. Most mosquitoes fly at dusk, especially in wooded areas near water. Activity is lower during the sunnier, hotter times of day.
  • Eliminate mosquito breeding areas. Mosquitoes lay their eggs in standing water. That could mean a puddle that never dries up in your lawn or flowerpots and garbage can lids where water accumulates and sits.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

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Alex Koliada, PhD

Alex Koliada, PhD

Alex Koliada, PhD, is a well-known doctor. He is famous for his studies of ageing, genetics and other medical conditions. He works at the Institute of Food Biotechnology and Genomics NAS of Ukraine. His scientific researches are printed by the most reputable international magazines. Some of his works are: Differences in the gut Firmicutes to Bacteroidetes ratio across age groups in healthy Ukrainian population []; Mating status affects Drosophila lifespan, metabolism and antioxidant system [Science Direct]; Anise Hyssop Agastache foeniculum Increases Lifespan, Stress Resistance, and Metabolism by Affecting Free Radical Processes in Drosophila [Frontiersin].
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