Cellulitis From a Bug Bite

Bedbug bites, mosquito bites, spider bites and fly bites can break your skin. Bacteria (usually strep or staph) can enter the skin, especially when you scratch an itchy bug bite. The bacteria can cause cellulitis, a skin infection that causes red, swollen skin and fever. Antibiotics can help.


What is cellulitis?

Cellulitis occurs when bacteria enter the skin, causing an infection. The infection may go deep into tissue and cause serious problems. Group A Streptococcus (strep) and Staphylococcus aureus (staph infection) bacteria are the most common causes of cellulitis. These bacteria enter the body through breaks in the skin.


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Can you get cellulitis from a bug bite?

Yes, you can get cellulitis from a bug bite. If you pick at or scratch an itchy bug bite, you provide an opening for bacteria to enter the skin and tissues. The bacteria may come from underneath your fingernails or another source.

Can a bug give you cellulitis?

An insect can’t give you cellulitis. There’s nothing in an insect’s saliva or venom that causes cellulitis. The bite can irritate your skin and make it itchy. When you scratch, bacteria can enter.


Is cellulitis contagious?

It’s uncommon for cellulitis to spread from one person to another. You may get the infection if an open wound comes into contact with fluid-filled blisters or pus from a person who has cellulitis. These fluids can contain the bacteria that cause infection.

Symptoms and Causes

What causes cellulitis?

Bacteria like strep and staph cause cellulitis. Breaks in the skin (from a wound or dry, cracked skin) let bacteria into tissue underneath the skin. The bacteria grow and multiply, causing an infection.


How do insect bites cause cellulitis?

Everyone has some amount of dirt and germs underneath their fingernails — even when fingernails look clean. When you cause an opening in the skin by scratching an itchy insect bite with your fingernails, germs on your skin or under your fingernails can enter.

Children who spend a lot of time outdoors playing may be more prone to getting cellulitis this way. But it can happen to adults, too. Even if you don’t scratch, the tiny opening from the insect bite can let germs in.

What are the risk factors for cellulitis from a bug bite?

Children spend more time outside and tend to get more bug bites than adults. Their fingernails are often dirtier, too. These factors increase a child’s risk for cellulitis.

If you have a weak immune system due to autoimmune disease, cancer or another illness, you may be more prone to cellulitis. The immune system helps your body fight off infections.

Other cellulitis risk factors include:

What bug bites cause cellulitis?

Any type of bug bite can lead to cellulitis. These include:

What are the symptoms of cellulitis from an insect bite?

Cellulitis often causes fever, chills and fatigue before you notice changes to the skin. Some people feel nauseous.

Cellulitis develops in the area where bacteria enter the skin. It can appear anywhere on the body. In adults, cellulitis often affects a leg or foot. In children, cellulitis more commonly affects the face and neck.

Signs of cellulitis include:

  • Redness, swelling, warmth or tenderness around the bite area.
  • Red streaks that shoot out from the bite area.
  • Blisters.
  • Swollen lymph nodes.
  • Yellow, pus-like discharge from the bite.

You can use a washable marker to draw a border around the red, swollen bug bite area to track its size. You should contact your healthcare provider immediately if redness, swelling or blisters expand outside this border. Your provider may monitor the bite infection this way to make sure the infection clears up with treatment and doesn’t get worse.

Diagnosis and Tests

How is cellulitis diagnosed?

Your healthcare provider can diagnose cellulitis by looking at the skin and assessing symptoms. Blood tests can identify the bacterial cause of the infection, but these tests aren’t usually necessary.

Management and Treatment

How is cellulitis managed or treated?

Cellulitis treatments include:

  • Antibiotics for seven to 14 days to get rid of the infection.
  • Proper wound care, including covering the wound to prevent further infection and promote healing.
  • Rest, elevating the affected area and applying cold compresses to reduce swelling.

What are the complications of cellulitis?

Cellulitis can be dangerous if the infection is severe or spreads. Some people need intravenous (IV) antibiotics in the hospital. You may develop a skin abscess that requires draining.

Rarely, these complications may occur:

  • Sepsis or bacteremia (blood infections).
  • Necrotizing fasciitis (flesh-eating bacterial infection).
  • Osteomyelitis (bone infection).


How can I prevent getting cellulitis from insect bites?

You can lower the risk of cellulitis from a bug bite by trimming fingernails and taking these steps:

  • Clean a bug bite with soap and water.
  • Take an over-the-counter oral antihistamine to relieve itching. This medicine may work better than a topical cream.
  • Apply an antibiotic ointment to the bite area if the skin is broken.
  • Cover the bite with a bandage to keep germs out and lower the temptation to scratch.
  • Apply fresh medication and bandages daily or anytime the area gets dirty.

How can I prevent insect bites?

To lower your family’s risk of insect bites:

  • Use an Environmental Protection Agency (EPA)-registered insect repellant.
  • Wear pants and long-sleeved shirts when outside.
  • Apply permethrin (an insecticide) to clothes.

Outlook / Prognosis

What is the prognosis (outlook) for people who have cellulitis?

Most people feel better after about five days of taking antibiotics. Severe cellulitis may last two weeks or longer. To completely get rid of the infection, it’s important to take all of the antibiotics, even if you start to feel better.

Sometimes, symptoms get worse for a few days after you start treatment. This worsening of symptoms may be the result of bacteria dying off.

Having cellulitis once increases your risk of getting the infection again, usually in the same area. People who have weak immune or lymphatic systems are most at risk for recurrent cellulitis.

Living With

When should I call the healthcare provider?

You should call your healthcare provider if you experience:

  • Fever, chills or nausea.
  • Signs of infection like redness or oozing.
  • Red streaks or blisters that shoot out from a bug bite.

What questions should I ask my healthcare provider?

You may want to ask your healthcare provider:

  • What’s the best treatment for me?
  • What are treatment side effects?
  • How can I lower my chances of getting cellulitis again?
  • Should I look out for signs of complications?

A note from Cleveland Clinic

It’s tempting to seek momentary relief by scratching annoying, itchy bug bites. But you can break open the skin and expose your body to bacteria that cause cellulitis. Children have an especially hard time not scratching insect bites. Contact your healthcare provider if you or a family member show signs of infection like fever and red streaks on the skin. Antibiotics are an effective treatment for cellulitis brought on by insect bites.

Medically Reviewed

Last reviewed on 05/04/2021.

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