Insects often bite humans in an attempt to feed or in self-defense. Most insect bites are harmless and disappear after a few days. However, in some cases, an insect bite may become infected.

Many insects will inject a person with formic acid when biting them. This saliva may contain several substances, some of which can cause a person’s body to respond adversely.

Various insects in the United States can bite. These include bedbugs, fleas, mosquitos, and more. Typically, insect bites do not require medical attention. However, in some instances, an insect bite may cause an allergic reaction but also become infected.

This article explains the symptoms of infected bug bites, how to treat them, and how to prevent them from becoming infected.

The skin acts as a barrier to the harmless bacteria on its surface. If the skin breaks, these harmless bacteria can get under the skin and cause an infection.

An insect bite can penetrate the skin, allowing bacteria to enter.

A common symptom of insect bites is a small, itchy lump. If a person scratches this lump, it may break the skin. This can allow bacteria from their hand to enter the bite, leading to an infection.

A person may have to see a doctor for treatment if they have an infected insect bite. However, most infected bites are easy to treat with a course of antibiotics.

Learn why mosquito bites itch.

An infected insect bite may cause one or more of these symptoms:

  • a buildup of pus
  • chills
  • a feeling of warmth around the bite
  • fever
  • increasing pain
  • a red or dark line extending from the bite
  • discoloration and swelling appearing around the bite
  • sores or abscesses on or around the bite
  • swollen glands (lymph nodes)

Insect bites can cause several common infections.

Learn more about different types of infection here.


Impetigo is a common and highly contagious skin infection. It is most common in young children; however, adults can get it too.

The first sign of impetigo is a patch of red or purplish, itchy skin. This can then develop into sores that burst and ooze before drying up.

Impetigo is easy to treat using antibiotics. According to the American Academy of Dermatology Association (AAD), the infection can cause new sores or blisters to develop if left untreated. The infection can also go deeper beneath the skin, which can be severe.

Learn more about what skin infections look like here.


Cellulitis is a relatively widespread bacterial infection that occurs in the deeper layers of the skin. An older 2016 article indicated that around 14.5 million people develop cellulitis in the U.S. each year.

Cellulitis can be very painful. It can involve skin discoloration and pain in one area and feels warm and tender to the touch.

The infection can spread rapidly around the body and can lead to sepsis, which is severe. Cellulitis can start suddenly and can become life threatening without quick treatment.

If caught early, a doctor will usually prescribe antibiotics to treat cellulitis. However, if the infection is more severe, it may require intravenous (IV) antibiotics and other care.

Learn more about cellulitis from insect bites here.


Lymphangitis is an infection of the lymph vessels. It is a secondary infection, meaning other infections cause lymphangitis to occur. Infections caused by insect bites can cause lymphangitis.

Early signs of lymphangitis include red or dark streaks extending from the bite to areas where lymph glands are present. These include the areas around the neck, armpits, groin, and gut.

Other lymphangitis symptoms include:

  • feeling sick or weak
  • chills
  • fever
  • headache
  • low energy
  • loss of appetite

Lymphangitis can be severe and may spread quickly. Anyone experiencing these symptoms must go to a doctor. A doctor will usually prescribe antibiotics to treat the issue. If IV antibiotics are necessary, the treatment may occur in the hospital or doctor’s office.

Learn more about the lymphatic system here.

Lyme disease

Lyme disease is the most common vector-born disease in the U.S. Infected black-legged ticks transfer this disease to humans through their bite.

Lyme disease symptoms include fever, headache, fatigue, and a rash on the person’s skin. If left untreated, the infection can spread to the heart, joints, and nervous system.

In most cases, a doctor will treat Lyme disease with antibiotics.

Learn more about tick bites here.

The most common treatment for an infected insect bite is a course of antibiotics. Depending on the severity of the infection, a doctor may prescribe oral or IV antibiotics. Doctors will administer IV antibiotics in the hospital or doctor’s office.

A person must take all of the prescribed antibiotics. It is essential not to skip any doses or stop before finishing the course, even if the symptoms have already improved.

Placing a cold compress on the insect bite, taking oral pain relief medication, or using an anesthetic cream can help ease any discomfort.

Learn about how to deal with insect and spider bites here.

There are several things a person can do to prevent insect bites. These include:

  • avoiding bothering insects
  • avoiding heavily scented cosmetics and bright-colored clothing
  • avoiding wooded and grassy areas
  • taking care when eating outside, as this may attract insects
  • using insect repellent
  • using structural barriers, such as window screens or netting, when indoors
  • wearing protective clothing if necessary

If an insect does bite, there are several things a person can do to prevent infection. These include:

  • applying ice compresses to the bite
  • cleaning the bite with soap and water
  • elevating the area if it becomes swollen
  • taking anti-inflammatory drugs
  • updating tetanus status as required

Learn how to identify an infected wound here.

Some people can have an allergic reaction to an insect bite. If this happens, a person should seek medical help. The main sign of an allergic reaction is swelling of the skin around the bite that lasts longer than 24 hours.

Here are some other signs of an allergic reaction to an insect bite:

It is worth noting that insect bites rarely cause allergic reactions. One study showed that just 2% of people react to insect bites and stings and display symptoms that affect more than only the surrounding area of skin.

An allergic reaction to an insect bite can be severe. When this occurs, a doctor may prescribe oral antihistamines or pain relievers.

Learn more about allergies here.

People should see a doctor if they believe they have an infected insect bite. Early treatment of the infection can prevent further complications.

A person should seek emergency medical help if they are showing signs of an infection and also have one of the following symptoms:

  • dizziness
  • hives and itching across the body
  • loss of consciousness
  • nausea or vomiting
  • swollen face, mouth, or throat
  • tight chest or throat
  • trouble breathing
  • trouble swallowing

A person should also seek emergency medical help if a poisonous insect or bug has bitten them.

Learn about five poisonous insects here.

Insect bites are common and are often not a cause for concern. They will usually go away after a few days without needing treatment.

A person should seek medical help from a doctor if their insect bite becomes infected. Treatment will typically involve a course of antibiotics. Early treatment can help prevent further complications and other infections.

If the infection is more severe, a person may require IV antibiotics or other care.