Cellulitis From Bug Bites: What You Should Know

Bug and spider bites may need antibiotic treatment if they turn into a skin infection called cellulitis. A bug or spider bite makes an open wound in the skin where bacteria can get in. This can lead to cellulitis, a serious medical problem that needs treatment as soon as possible. 

This article will explain when bug and spider bites need antibiotics for cellulitis and what other treatment you may need if a bite gets infected. 

What Is Cellulitis?

Cellulitis is a skin infection that goes into deeper areas of the skin (subcutaneous tissue). It causes symptoms like redness, swelling, and tenderness in the affected area of the skin.

The most common cause of cellulitis is bacteria called group A Streptococcus. Staphylococcus aureus can also cause cellulitis and usually causes a pus-like discharge from the infected wound. 

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

Since bug bites happen on the skin, they can cause cellulitis. But cellulitis can also develop from other skin injuries like cuts, needle sticks, as well as wounds after surgery. People with chronic skin conditions (like eczema) or brief illnesses that affect the skin (like shingles) can also get cellulitis. 

Some people are more at risk for getting cellulitis from a bug or spider bite, including those who:

• Are older 
• Have obesity
• Have a history of lymphedema (poor drainage of the lymphatic system that moves fluid from the distal parts of the body to the center)
• Have a history of peripheral vascular disease
• Have a history of diabetes
• Have a weakened immune system 
• Chronically use corticosteroids

If left untreated, cellulitis can spread to other parts of the body and can even be life-threatening. Oral antibiotics need to be taken as soon as possible to clear up the infection and prevent complications. 

How Is Cellulitis Caused By a Bug Bite?

Most bug bites do not get infected or lead to cellulitis but it’s important to know about the risk. The bacteria that cause cellulitis do not come from the bug that bit you. Bug and spider bites make breaks in the skin; bacteria that often hang out on human bodies and are harmless can get into the body through the opening. Once inside, the bacteria can lead to an infection.

Bacteria like group A Streptococcus and Staphylococcus aureus are common in the environment and on your skin. If they get into your body through a bug or spider bite, you could develop cellulitis. 

Scratching or picking at a bite can make an infection more likely since you are opening up the skin even more.

What Are the Symptoms of Cellulitis From a Bug Bite?

Bug bite infection symptoms vary according to the type of infection and how bad it is, as well as which insect bit you. As bacteria multiply in the skin, symptoms of cellulitis start to show up. Cellulitis from a bug or spider bite can cause:

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

If you have a bad infection, the bite may have yellow drainage. Sometimes, the pus-like material collects under the skin to form a pocket (abscess). As the infection gets worse, other symptoms might develop like fatigue, chills, or a fever.

How Is Cellulitis From a Bug Bite Treated?

Cellulitis from a bug or spider bite will need to be treated by a healthcare provider. There are also some things you can do at home to help the bite heal. 

Medical Treatments

You may need topical, oral, or intravenous (IV) antibiotics for a bug bite infection. 

• Cellulitis is usually treated with seven to 10 days of antibiotics. The choice of antibiotic depends on the type of infection, antibiotic resistance patterns in the local community, and the severity of the infection. Typically, providers will choose a penicillin-based antibiotic or a cephalosporin for cellulitis. 
• If a Staphylococcus aureus infection is causing the infection, a provider will also need to think about the chances of a methicillin-resistant Staphylococcus aureus (MRSA) infection. In this situation, the most effective antibiotics are clindamycin, trimethoprim-sulfamethoxazole, doxycycline, linezolid, or vancomycin.

You may also need to take other medications to help with pain and swelling while you are waiting for antibiotics to work. For example, Tylenol (acetaminophen) is an effective over-the-counter (OTC) pain reliever. Ibuprofen can also treat pain as well as provide anti-inflammatory effects that can treat redness and swelling.

Home Remedies

Natural remedies often claim to have wound-healing effects, but these remedies have not been proven to treat an infection in high-quality research studies.

If you have cellulitis from a bug or spider bite, you need medical treatment. In addition, your provider may also recommend some steps you can take at home to help your skin heal. 

If you just have a minor infection, your provider might ask you to try OTC topical antibiotic ointments, like bacitracin or triple antibiotic therapy. However, research has not shown any difference when using ointments instead of just using basic wound care to treat a minor skin infection.

What Antibiotics Treat Spider Bite Infections?

The antibiotics for cellulitis from a spider bite infection will depend on several factors, like the severity and what medication would be the safest and most effective. Your provider will also consider your risk of having an infection that is resistant to treatment.

Cephalexin, sulfamethoxazole-trimethoprim, or clindamycin are usually the choices of antibiotics that can treat cellulitis, including when it's from a spider bite.

Additional Type of Bug Bites Infections

Bug bites can lead to other skin infections and complications from those infections, such as:

• Impetigo
• Lymphangitis
• Abscess
• Folliculitis

Less commonly, bug and spider bites can lead to:

• Necrotizing fasciitis ("Flesh-eating bacteria")
• Erysipelas ("St. Anthony's Fire")

Impetigo

Impetigo is a minor infection of the outermost layer of the skin. This infection is most commonly caused by group A Streptococcus. It looks like tiny, pimple-like lesions on the skin. The lesions break over a few days, leaving a crusty golden area around the bug bite. Impetigo typically does not lead to any other symptoms.

Treating impetigo usually does not require oral antibiotics. If it does, topical therapy is often all that is needed. A provider will most likely prescribe mupirocin or retapamulin.

Lymphangitis

Lymphangitis is a streaking redness that looks like it is spreading out from an infected bug bite with cellulitis. The streaking redness shows the spread of infection along a drainage system called the lymphatic system. The drainage moves toward the lymph nodes that are helping fight the infection.

Lymphangitis is often associated with serious symptoms like fever, chills, muscle aches, and malaise. It generally means that cellulitis is getting worse and is spreading through the body. 

Treatment should start right away. Sometimes, IV antibiotics are used instead of oral antibiotics. The same antibiotics that are used to treat cellulitis are used to treat lymphangitis, but it is more likely that a person will require IV treatment if they have an infection that is spreading.

Abscess

An abscess is a collection of pus under the skin. If a bug or spider bite gets infected, the pus can build up and be walled off under the skin and form an abscess. It usually looks red and like a pimple, and can be painful or warm if you touch it.

An abscess is an infection that needs medical care. You may need to take antibiotics and a provider might have to open the abscess so it can drain. You should never try to "pop" or cut open an abscess on your own at home.

Folliculitis

An infected hair follicle is called folliculitis. It usually causes pus-filled bumps on the skin that can hurt. Folliculitis happens when hair follicles get blocked or damaged, like from too-tight clothes or a trauma. If a bug bite is near a hair follicle, it may irritate it.

Folliculitis usually gets better on its own. If it doesn't or if it's caused by an infected bug bite, you may need antibiotics. Your provider also may need to drain any pus-filled bumps so they can heal.

Necrotizing Fasciitis

Necrotizing fasciitis is a serious skin infection that goes deep into the skin and tissues. Sometimes, it's called "flesh-eating bacteria" because some forms of it cause the skin to die. It's not common, but an infected insect or spider bite that is not treated could lead to necrotizing fasciitis.

If you develop this serious infection from a bug bite, you need medical treatment right away because it can spread very quickly, become very serious, and can even be fatal.

Erysipelas

Erysipelas is a skin infection that's caused by Streptococcus pyogenes bacteria. A bite from an insect makes an opening in the skin for the bacteria to get inside and cause an infection. It usually causes bright-red skin that hurts, which is why it has the nickname "St. Anthony's Fire."

Erysipelas can be treated with antibiotics and OTC pain relievers.

Can You Be Allergic to Bug Bites?

Some bug bites that cause serious skin reactions could be an allergic reactions rather than an infection. Rarely, allergic reactions to bug or spider bites are life-threatening.

Allergic reactions to insect saliva come on much faster than an infection. The skin will often swell a lot, and a person can get hives. The bitten area will also be itchy.

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

Prevention

The best way to prevent a bug or spider bite infection is to do what you can to avoid being bitten. Here are a few tips for preventing bug and spider bites:

• 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 gentle 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 help with itching.

Research does not suggest that people need to prophylactically (preventatively) use topical antibiotics or take pills to prevent an infection. However, researchers do not agree on whether people who get frequent skin infections should use prophylactic antibiotics.

If you are someone who often gets a skin infection after a bug bite or another break in your skin, talk to your provider about whether you need prophylactic antibiotics.

When to See a Healthcare Provider

An infected bug bite usually needs antibiotic treatment. It can be hard to know if a bug or spider bite is swollen and red because of inflammation from your immune system’s normal response, or whether you have an infection. 

Remember: An infection does not happen immediately, and can take time to develop after a bug bite. If the redness, swelling, and pain increase after cleaning and managing the wound at home, call your healthcare provider.

Summary

If you have cellulitis from a bug or spider bite, you will need to take antibiotics. Your provider will recommend the antibiotic that is safest and most effective for you to take. 

Bug and spider bites do not usually get infected, but it’s important to know the signs of an infection and get medical treatment. You should also take steps to avoid bug and spider bites, whether you’re at home or enjoying the outdoors.