Infected Bug Bite: What You Should Know

Bug bites are an all too common annoyance. They can not only ruin an evening outdoors, but, more seriously, they can lead to a range of infections in severe cases. When a bug bites a person and breaks the skin, bacteria that is usually harmless can enter the body and cause problems. Most bug bites do not require any medical intervention, but sometimes the bacteria can multiply and lead to an infection.

This article discusses the different types of skin infections from bug bites, treatment and prevention, and when to call your healthcare provider.

Bug Bite Prevention - Illustration by Jessica Olah

Verywell / Jessica Olah

Why Do Bugs Bite?

There are a few different reasons bugs bite people, and some people are more attractive than others.

Mosquitoes are attracted to the scent of a specific protein released in bodily fluids and saliva. People with type O blood are more likely to secrete these delectable proteins.

Bugs also bite because of body odor produced by the bacteria that usually reside on the skin. Additionally, dark clothing seems more attractive, as does a person who recently ingested alcohol.

Bugs bite a person by piercing the skin using a mouthpart, called a proboscis. This mouthpart allows them to suck up nutrients from the blood when they bite a person. When the bug’s saliva is injected into the body, the immune system recognizes the saliva proteins as foreign to the human body.

The immune system's inflammatory reaction for fighting foreign substances is the swelling and redness that a person develops around the bug bite. The size of the inflammatory response depends on the individual.

Causes of a Bug Bite Infection

All bug bites can lead to infection because they are caused by breaks in the skin. Fortunately, most bug bites do not become infected.

Bugs that people typically encounter include:

  • Fleas
  • Mosquitos
  • Ticks
  • Bedbugs
  • Flies
  • Spiders

The most common bacterial organisms that cause a skin infection after a bug bite are group A Streptococcus and Staphylococcus aureus. These bacteria are generally found in the environment and on the skin. They can enter the body when the bite of a bug punctures it. The bacteria do not come from bug saliva.

The bacteria can also enter the body when a person scratches at the bite, since scratching also breaks the skin.

Is it MRSA?

According to the Centers for Disease Control and Prevention, 33% of the population is colonized with Staphylococcus aureus, but approximately 1% of people are colonized with methicillin-resistant Staphylococcus aureus (MRSA).


Bug bite infection symptoms vary according to the type of infection and its severity, as well as what organism caused the bite.

As bacteria multiply in the skin, symptoms include:

  • Redness
  • Swelling
  • Warmth in the area
  • Tenderness
  • Blistering
  • Bruising
  • Golden crusts around the bite
  • Red streaks that move away from the bite area
  • Swollen lymph nodes

A severe infection might show significant yellow drainage. Sometimes, the pus-like material collects underneath the skin to form an abscess.

People can also develop fatigue, chills, or a fever as the infection worsens.

Types of Infections

Several different types of skin infections can occur after a bug bite. These include:

These are all most commonly caused by the same organisms and differ based on the layer of the skin that is infected, or how deep the infection goes.

Diagnosing Bug Bite Infections

A healthcare provider can diagnose these skin infections based on how they look during a physical examination. They can then prescribe antibiotics for any that require such treatment.


Impetigo involves the outermost layer of the skin.

This type of infection is most commonly caused by group A Streptococcus. It is identified by tiny lesions that look like pimples. The lesions break over a few days, leaving a crusty golden area around the bug bite.

Impetigo is considered the most minor skin infection, and it typically does not lead to any other associated symptoms.

Treating impetigo can sometimes call for antibiotics, but generally, topical therapy is all that is required.


Cellulitis is the most classic skin infection that occurs after a bug bite. It involves the deeper areas of the skin called the subcutaneous tissue, and leads to redness, swelling, and tenderness in the area.

The most common cause of cellulitis is group A Streptococcus. Another cause is Staphylococcus aureus. If staph is the cause, there is often pus-like drainage present. 

Cellulitis can appear anywhere on the body but it is most commonly found on the feet and legs. Since it is a deeper infection than impetigo, it can involve more extensive areas of the skin. People can also develop fever, chills, and malaise.

Certain people are more prone to developing cellulitis after a bug bite, including people who:

If left untreated, cellulitis can spread to other parts of the body. Therefore, oral antibiotics are recommended when an infection is present.


Lymphangitis presents with a streaking redness that radiates outward from an infected bug bite with associated cellulitis. This streaking redness represents the spread of infection along a drainage system called the lymphatic system. The drainage moves towards lymph nodes that are helping to fight the infection.

Lymphangitis is often associated with more significant symptoms like fever, chills, muscle aches, and malaise. It generally means that cellulitis is getting worse and spreading.

Treatment should begin right away, and sometimes intravenous antibiotics are recommended instead of oral antibiotics.


Home Remedies

Several natural remedies are advertised as wound healing substances, but none of them been proven to treat an actual infection in high-quality research studies.

Additionally, people might use other over-the-counter topical antibiotic ointments, like bacitracin or triple antibiotic therapy, to prevent or treat a skin infection. However, research studies do not show any difference when people use these ointments vs. clean, regular wound care to treat a minor superficial infection.

Do I Need Antibiotics?

Generally, the body can fight a minor infection on its own without antibiotics. Keeping the area clean and loosely covered may be enough. However, your healthcare provider will make this determination during the diagnostic process.

Medical Treatments

Skin infections are typically treated with topical, oral, or intravenous antibiotics depending on the severity of the condition.

  • Impetigo is treated with topical or oral antibiotics. A healthcare provider will most likely initially recommend mupirocin or retapamulin. 
  • Cellulitis is usually treated with a seven to 10 day course of antibiotics. The choice of agent depends on the type of infection, antibiotic resistance patterns in the local community, and the severity of the infection. Typically healthcare providers will use a penicillin-based antibiotic or a cephalosporin. 
  • If a Staphylococcus aureus infection is suspected, the healthcare provider will also need to weigh the likelihood of a methicillin-resistant Staphylococcus aureus (MRSA) infection. In this situation, the most effective antibiotics are clindamycin, trimethoprim-sulfamethoxazole, doxycycline, linezolid, or vancomycin.
  • The same antibiotics used to treat cellulitis are used to treat lymphangitis, but it is more likely that a person will require intravenous treatment instead.

Patients can also take other medications to help with pain and swelling. Acetaminophen is an effective pain reliever. Ibuprofen can also treat pain, but it also functions as an anti-inflammatory that can treat redness and swelling.

Allergic Reactions to Bug Bites

Some bug bites that develop significant skin reactions could be the result of an allergic reaction rather than an infection. Rarely, these allergic reactions become life-threatening.

Allergic reactions to insect saliva occur much faster than an infection. The skin will often swell significantly, and a person can develop hives. The bitten area will also itch a lot.

Treating an allergic reaction starts with ice and topical anti-itch creams, like hydrocortisone or antihistamines. If the allergic reaction is more severe, a person will need to see a healthcare provider for systemic steroid medication. If a person develops anaphylaxis, they will need a shot of epinephrine.

Watch for Anaphylaxis

If the allergic reaction affects the entire body, it can lead to a life-threatening syndrome called anaphylaxis. Symptoms of a more severe reaction include:

  • Dizziness
  • Nausea and vomiting
  • Itching over the entire body
  • Wheezing and shortness of breath

As the allergic reaction gets worse, blood pressure starts to drop, and a person might lose consciousness. They might even go into cardiac arrest. These symptoms occur soon after a person is bitten.


The best way to prevent a bug bite infection is to prevent bug bites altogether. Some ways you can do this include:

  • Use insect repellent
  • Wear long shirts and pants in outdoor areas
  • Treat clothing and gear with permethrin
  • Control the bugs and mosquitoes in your environment
  • Use mosquito netting when sleeping (where applicable)

The best way to prevent an infection after you've already been bitten is by washing the area with regular soap and water. Keep the area covered with a clean, dry bandage. Apply ice packs to help with swelling and itching.

Topical therapies like baking soda and water paste, hydrocortisone cream, or Benadryl cream can also reduce itching.

Prevent the Itch

Remember, itching also breaks the skin, so avoiding the itchy area can prevent infection.

Research does not suggest that people need to prophylactically use topical antibiotics or take pills to prevent an infection. However, scientists are conflicted on whether people who develop frequent skin infections should use prophylactic antibiotics.

If you are someone who often develops a skin infection after a bug bite or other break in the skin, speak to your healthcare provider about whether you need prophylactic antibiotics.

When to Contact Your Healthcare Provider

An infected bug bite usually requires antibiotic treatment. The difficulty is knowing whether a bug bite is swollen and red because of inflammation from the immune system fighting the foreign protein, or whether a person truly has a bacterial infection.

Infection does not happen immediately, and can take some time to develop after a bug bite. If the redness, swelling, and pain continue to increase after cleaning and managing the wound at home, contact your healthcare provider.


Bug bites are common. Localized swelling and redness can initially occur from the inflammatory reaction to the bug saliva. To prevent infection, keep the site clean and covered. If an infection does occur, see a healthcare provider for prescription antibiotic therapy. There are no over-the-counter or home remedies that treat an actual skin infection.

A Word From Verywell

Though bug bites can ruin an evening, fortunately they do not typically have any complications. Try to prevent bug bites by using bug spray and wearing long clothes, and if you do get bitten, make sure you keep it clean and covered. If you are ever concerned about a possible infection, reach out to your healthcare provider as soon as possible.

Frequently Asked Questions

  • How long does it take for an infected bug bite to heal?

    An infected bug bite will start to improve two to three days after you begin taking antibiotics. Your healthcare provider will most likely prescribe seven days of treatment.

  • What antibiotics treat infected bug bites?

    The choice of antibiotic depends on the type of infection, resistance patterns, and infection severity. Mupirocin treats impetigo. Your healthcare provider will most likely use cephalexin, sulfamethoxazole-trimethoprim, or clindamycin to treat cellulitis, depending on your risk for a resistant organism.

  • How do I tell the difference between an allergic skin reaction and a skin infection after a bug bite?

    Redness and swelling occur after bug bites. If the swelling quickly worsens, is associated with a rash elsewhere on the body, and causes intense itching, it's probably an allergic reaction. However, if the swelling worsens over time and starts to hurt or show a yellow crust, it's probably infected.

11 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.
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  2. Centers for Disease Control and Prevention. Mosquito bite symptoms and treatment.

  3. Centers for Disease Control and Prevention. MRSA and the workplace.

  4. Cleveland Clinic. Cellulitis from a bug bite.

  5. Stevens DL, Bryant AE, University of Oklahoma Health Sciences Center. Impetigo, erysipelas and cellulitis.

  6. Centers for Disease Control and Prevention. Cellulitis: all you need to know.

  7. MedlinePlus. Cellulitis.

  8. MedlinePlus. Lymphangitis.

  9. Williamson DA, Carter GP, Howden BP. Current and emerging topical antibacterials and antiseptics: agents, action, and resistance patterns. Clin Microbiol Rev. 2017;30(3):827-860. doi:10.1128/CMR.00112-16

  10. Centers for Disease Control and Prevention. Impetigo: all you need to know.

  11. Institute for Quality and Efficiency in Health Care. Insect venom allergies: overview.

By Christine Zink, MD
Dr. Christine Zink, MD, is a board-certified emergency medicine with expertise in the wilderness and global medicine. She completed her medical training at Weill Cornell Medical College and residency in emergency medicine at New York-Presbyterian Hospital. She utilizes 15-years of clinical experience in her medical writing.