What You Should Know About Cellulitis From a Bug Bite

Sometimes bug bites can become infected, leading to conditions like cellulitis. Cellulitis is a bacterial infection of the dermis, the thick middle layer of skin. It occurs when bacteria enter the dermis through a break in the skin, like the openings caused by insect bites. This can lead to a bug bite getting bigger and redder, as well as other cellulitis symptoms like inflammation and fever. 

Continue reading to learn more about cellulitis from a bug bite, its causes, and cellulitis treatment. 

mosquito arm insect bite keystone virus

Janosa Kerekes / Getty Images

What Is Cellulitis?

Cellulitis is a bacterial infection of the dermis. The dermis is the middle layer of skin, between the epidermis and subcutaneous tissue. Cellulitis occurs when bacteria reach the dermis through openings in the skin. 

Cellulitis is very common, affecting more than 14 million Americans each year. It can happen to anyone who has an injury to their skin. However, it’s most common in:

  • Adults who are middle age or older
  • People who are overweight
  • People with diabetes, especially if their blood sugars are poorly controlled.

How Bug Bites Cause Cellulitis

Bug bites puncture the skin, leaving it vulnerable to bacteria and other pathogens. Cellulitis is most often caused by Streptococcus and Staphylococcus aureus bacteria. Bugs don’t carry these bacteria, but once a bug punctures your skin with a bite, the bacteria can enter your body if you’re exposed to them. Many healthy people have these bacteria on their skin or in their noses and mouths. They don’t usually cause infection in those areas, but can lead to cellulitis if they reach the dermis. 

Scratching bug bites leads to more openings in the skin, and may increase your risk for cellulitis. Instead, find other ways to stop itching, like using a cold compress. 


If a bug bite develops cellulitis, you’ll notice symptoms including redness and swelling. The bite will be painful or tender to the touch and may feel warm. These are common symptoms of cellulitis. In addition, you may develop red streaks running to and from the bite. If the infection is severe, you might experience fever, chills, and swollen lymph nodes.  


If cellulitis is left untreated, the infection can spread throughout your body, affecting your:

  • Blood
  • Joints
  • Bones
  • Heart

In rare cases, cellulitis can lead to necrotizing fasciitis, a severe infection that causes soft tissue to die. This can be fatal if it’s not treated quickly. 

Although the complications of cellulitis are rare, they can be very serious. It’s best not to delay care. Call your healthcare provider immediately if you suspect cellulitis from a bug bite. 


Usually, healthcare providers diagnose cellulitis just by looking at the affected area. When you see a healthcare provider, you should mention that you’ve recently had a bug bite. This may help them diagnose you and rule out other bacterial skin infections

Ways to Treat Cellulitis From a Bug Bite

Cellulitis is treated using antibiotics. These are medicines that kill bacteria, including those that cause cellulitis. Most people will take oral antibiotics for ten days, but will begin to feel better after a day or two. 

As your infection clears up, you’ll notice that the area becomes less swollen, sensitive, and red. Still, it’s important to finish your entire prescribed course of antibiotics, even if the infection disappears entirely. This ensures that all the bacteria are cleared away so they don't come back. 

If you have a severe infection or one that has spread beyond your dermis, your healthcare provider might order intravenous antibiotics. These are given via an IV right into your vein, and start fighting the infection sooner. 


Cellulitis is common and there’s no way to prevent it entirely. However, there are ways to reduce your risk:

  • Use insect repellent regularly to reduce your risk of a bite. 
  • If you notice a bite, wash it with soap and water.
  • Avoid scratching, which can increase damage to your skin and provide more openings for bacteria.
  • After getting a bug bite, keep the area elevated if possible.

When to See a Healthcare Provider

Cellulitis is always treated with antibiotics. These medications must be prescribed by a doctor. Anytime you suspect that you have cellulitis, you should see your healthcare provider. 

It’s always a good idea to keep a close eye on insect bites, and see a healthcare provider if you have:

  • A bite that gets worse, not better, with time
  • Symptoms like redness and swelling that last a week or more
  • A large area of redness or a rash
  • Pain at the bite sight
  • Fever, swollen lymph nodes, or other signs of infection.

Other Causes of Cellulitis

In addition to bug bites, cellulitis can be caused by:

  • Animal bites, including cat and dog bites
  • Tattoos or piercings
  • Intravenous drug use 
  • Recent surgery or injury leading to cuts or ulcers
  • Chronic skin conditions including athlete’s foot and eczema
  • Chicken pox or shingles


Cellulitis is a common infection of the dermis, the middle layer of skin. It happens when a cut or other opening in the skin allows bacteria to reach the dermis. Sometimes, cellulitis can occur after a bug bite, bringing symptoms including redness, pain, fever and chills. Cellulitis must be treated with antibiotics, so you should see your healthcare provider if you suspect that you have cellulitis. 

A Word From Verywell 

In most cases, bug bites are not cause for concern. However, they can sometimes lead to infections like cellulitis. It’s always best to reach out to your healthcare provider if you’re concerned in order to protect yourself.

Frequently Asked Questions

  • Is cellulitis contagious?

    Cellulitis is not contagious. In theory it could be passed if pus from someone with cellulitis found its way into a cut on another person, but this would be very unlikely. 

  • Does cellulitis go away on its own?

    No, cellulitis must be treated with antibiotics. If you suspect you have cellulitis, you should see your healthcare provider.

  • What does cellulitis look like?

    Cellulitis causes a red, inflamed patch on the skin. You might notice red lines running to or from the bite that has become infected. The area may also be warm or painful to the touch.

  • Can insect bites cause sepsis?

    Sepsis occurs when an infection moves into the blood. If cellulitis from a big bite is left untreated, it could lead to sepsis in rare cases. Because of that, it’s always best to be proactive about getting treatment for cellulitis. 


6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Cellulitis: Everything you need to know

  2. American Academy of Dermatology Association. Cellulitis: Diagnosis and treatment.

  3. Johns Hopkins Medicine. Cellulitis.

  4. National Organization for Rare Diseases. Necrotizing fasciitis.

  5. National Health Service. Insect bites and stings.

  6. Merck Manual Professional Version. Sepsis and septic shock.

By Kelly Burch
Kelly Burch is has written about health topics for more than a decade. Her writing has appeared in The Washington Post, The Chicago Tribune, and more.