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Bacteria on the Skin: Possible Health Benefits and Infections

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

A baby already has bacteria living on his or her skin.

A baby already has bacteria living on his or her skin.

Bacteria in and on the Body

Many people believe that bacteria living in or on our body must be bad for us. In reality, most of the trillions of bacteria that share our body with us have either a beneficial or a neutral effect on our lives. In fact, it would be difficult to survive if all of our microbes disappeared. Most of the microbes live in our digestive tract, but a large population lives on the skin.

Most of the microscopic organisms that reside on (or in) the skin are bacteria. The majority of these organisms are harmless. Some are harmless most of the time but can cause a problem under certain conditions. These conditions include a skin injury that allows them to penetrate deeper into the body than they would normally travel. Some of our skin bacteria may actually be helpful. Transient bacteria that we pick up from the environment may not be so benign, however. This article focuses on some of the effects of skin bacteria on our lives.

Resident and Transient Bacteria on the Skin

Resident Microbes

The resident bacteria on the skin are sometimes known as the skin flora and are said to form the skin microbiome. They feed on dead skin cells, chemicals released by living cells, and sebum. Sebum is an oily substance made by sebaceous glands. Its chief function is to lubricate and waterproof the skin. Resident bacteria are our long-term companions and aren't removed by washing with soap and water. They generally live deeper in the skin than transient ones. They can be removed with certain antibacterial chemicals.

Transient Microbes

Transient bacteria are those that we pick up when we touch contaminated surfaces. They aren't as firmly integrated with our skin as our resident bacteria and can be removed by washing with soap and water. Transient bacteria are more likely to be harmful than resident ones. When health experts tell us to wash our hands to prevent infections, they are often thinking about the potentially dangerous transient bacteria that may come into contact with our skin.

The identity of the bacteria that live on and in our skin depends on the habitat. Dry skin, oily areas, and areas that tend to stay moist (such as the skin between the toes) contain different bacterial communities. Fungi also live on our skin.

Resident Skin Bacteria May Boost Immunity

Resident skin bacteria are often classified as commensals. Commensalism is a relationship in which one organism benefits from the association and the other is unaffected. Mutualism may be a better name for the relationship between some skin bacteria and us, however. In mutualism, both organisms benefit from their association.

Recent evidence is showing that bacteria living on the skin may help us. The evidence suggests that some may protect us from pathogens (microbes that cause disease) by stimulating the activity of our immune system and possibly by making antimicrobial chemicals. The immune system's job is to fight disease.

A stained specimen showing Leishmania inside a bone marrow cell

A stained specimen showing Leishmania inside a bone marrow cell

Protection From Leishmania

Researchers at the National Institute of Allergy and Infectious Diseases (NIAID) have performed an interesting experiment in mice. The experiment demonstrated the protective role played by one type of skin bacterium. The mice were germ-free and had no microbes in their gut or on their skin, the most common sites for bacteria in both mouse and human bodies.

The researchers added a bacterium called Staphylococcus epidermidis to the skin of some of the germ-free mice. The bacterium multiplied and colonized the skin of the mice. The researchers then added a protozoan parasite called Leishmania major to the skin of the germ-free mice that had been given Staphylococcus and to the skin of germ-free mice without Staphyloccus. The mice with Staphylococcus were able to fight Leishmania; the mice without the bacterium were unable to fight the parasite.

Leishmania is also a parasite on human skin and Staphylococcus epidermidis is part of our skin flora. The researchers suspect that the results of their experiment with mice would be the same if the experiment was performed on human skin. They don't know whether this would be the case, however.

In humans, Leishmania causes a disease called leishmaniasis. The most common type of the disease is restricted to the skin and is called cutaneous leishmaniasis. Visceral leishmaniasis affects the internal organs and is a very dangerous disease.

Staphylococcus aureus, a common bacterium on human skin

Staphylococcus aureus, a common bacterium on human skin

Protection From a Fungal Infection

The same team that studied the relationship between Staphyloccus epidermidis and Leishmania has reported another interesting discovery about the bacterium. Once again, the study was performed in mice.

Once Staphyloccus epidermidis had colonized the skin of the mice, the researchers found an increase in the number of CD8+ T cells in their body. These T cells are part of the immune system in both mice and humans. The cells produce signaling molecules that stimulate other cells in the immune system and cause them to spring into action.

After the T cell level had risen, the researchers applied a pathogenic fungus to the skin of the mice. The mice were able to destroy the fungus. If the T cell and signaling molecule levels were reduced, the mice were unable to fight the pathogen.

Be Careful

Some skin bacteria appear to be helpful, but researchers know that others are potentially harmful. The information about human skin infections given below is intended for general interest. Anybody with a skin problem that concerns them should visit a doctor for a diagnosis and treatment recommendations.

Folliculitis Facts

One human skin problem caused by bacteria is folliculitis, or inflammation of the hair follicles. A hair follicle is a structure in the skin that produces a hair. It can become inflamed by either a bacterial infection or an irritation. Folliculitis is most common where skin is damaged. Insect bites, shaving cuts, or friction as the skin is rubbed repeatedly against clothing are some ways in which this damage may occur.

The disorder causes groups of small, red bumps to appear on the skin. The skin may also be itchy. If an infection is present, pimples filled with pus may form. Mild folliculitis may not need any treatment. Doctors may prescribe antibiotic creams or tablets for more serious cases.

The video above describes Folliculitis decalvans, a rare disorder in which inflamed hair follicles on the scalp are accompanied by patches of hair loss, or alopecia. The cause isn't known, but it may sometimes be due to an abnormal reaction to Staphylococcus aureus. This bacterium is a normal inhabitant of the skin in many people. In specific circumstances, previously harmless skin organisms can cause problems.

Boils or Furuncles

Like some cases of folliculitis, a boil is produced due to an infection of hair follicles. In this case, however, the infection goes deeper into the skin and a large, painful swelling filled with pus develops over the infected area. Boils are also called furuncles. The medical professional in the video above describes the problem.

The Mayo Clinic says that small boils can "generally" be treated at home. Home treatment includes applying warm compresses to the boil for ten minutes at a time, three or four times a day. When the boil has ruptured, it should be covered with a sterile dressing. It's important to be careful at this stage, since the fluid from the boil contains bacteria which can infect new areas. If a boil is soft, it may not burst on its own. This type of boil requires medical treatment.

A carbuncle is a cluster of boils that are positioned close together. Carbuncles often cause more discomfort than single boils and may be harder to treat.

Impetigo Information

Impetigo is a very contagious skin infection that is most common in young children. Red sores or blisters may appear on the face—especially around the nose and mouth—and on the neck, hands, forearms, or diaper area. Impetigo may develop on undamaged skin, but it usually appears on skin that has been irritated by being scratched after another injury, such as an encounter with poison ivy.

Large blisters are produced in bullous impetigo, while crusted sores are produced in non-bullous impetigo. Non-bullous impetigo is the most common type. Stapyhlococcus aureus can cause either type of impetigo. Non-bullous impetigo may also be caused by a form of Streptococcus.

Impetigo can be spread from one part of the body to another or from one person to another by skin contact. Touching materials like wash cloths, towels, or clothes that have come into contact with the sores can also transmit the disease. Impetigo is often treated with an antibiotic cream or with an antibiotic medication that is swallowed.


Cellulitis is an infection of the tissues below the surface of the skin. It is often treated by antibiotics. It's potentially dangerous because the bacteria may enter the blood or lymph nodes under the skin and then spread through the body. It's important to begin treatment as soon as possible.

Streptococcus and Staphylococcus are common causes of cellulitis. Unfortunately, MRSA (methicillin-resistant Staphylococcus aureus) also causes cellulitis. This bacterium is hard to treat because it's resistant to many common antibiotics, including methicillin. It's a different variety of bacterium from regular Staphylococcus aureus.

Risk Factors for Cellulitis

Factors that increase the risk of cellulitis development include:

  • a prior injury that has damaged the skin, making it easier for bacteria to penetrate the deeper layers of the skin
  • disorders that weaken the protective barrier of the skin, such as eczema and psoriasis
  • certain health problems, such as diabetes and disorders that weaken the immune system
  • being an older adult

Possible Symptoms of the Disorder

Some possible symptoms of cellulitis are mentioned below.

  • The infected area may be red, warm, swollen, and tender. These symptoms may occur in other conditions besides cellulitis, but they are a warning sign and should be watched very carefully.
  • If the red and swollen area is expanding, see a doctor very soon.
  • If the red and swollen area is rapidly getting worse, see a doctor immediately.
  • If a fever is present as well as a red and swollen area, see a doctor immediately.

Bacteria and Acne

Propionibacterium acnes is a normal inhabitant of most people's skin. It lives within the hair follicles instead of on the surface of the skin. The bacterium feeds on fatty acids in sebum, chemicals made by cells, and cellular debris. It may also be found in our gastrointestinal tract. Like other bacteria in our body, Propionibacterium acnes is metabolically active. It releases digestive enzymes and other chemicals and alters the environment around it.

Despite its activities, the microbe is usually a harmless member of our bacterial community. However, like some other skin bacteria it may occasionally cause problems. During adolescence, the amount of sebum that's made increases as a response to hormonal changes. This may cause a corresponding increase in the population of Propionibacterium acnes. At high levels, the bacterium can cause inflammation and play a role in the development of acne.

Washing the hands before and after certain situations is very important.

Washing the hands before and after certain situations is very important.

A person shouldn't be reluctant to wash their hands because of the fear of removing helpful resident bacteria . Experts say that ordinary hand washing won't affect these microbes because they are an integral part of the skin. If a doctor recommends a deeper or more thorough cleaning of the skin, their advice should be followed.

Wash Your Hands

Hand hygiene is very important, especially in some situations, such as an outbreak of disease in a community. Like skin bacteria, most bacteria in our intestine are helpful or harmless, but some dangerous bacteria may be present. These can be released in feces. Fecal bacteria can easily be transferred to our hands when we use a toilet or a public washroom. Washing the hands immediately in these situations is extremely important. Washing the hands before eating is also important in order to remove any harmful transient bacteria that we've picked up by touching objects.

It's also necessary to wash the hands after coming into a contact with certain skin problems caused by bacteria. The bacteria are often behaving abnormally or are located in an unusual habitat (for them) and can sometimes be transferred from one person to another.

Washing the hands is so important for health that the CDC website (Centers for Disease Control and Prevention) has a special section for the activity. A link to this section is provided in the "References" section below. Washing the hands with soap and water or with hand sanitizer and using correct technique can remove bacteria as well as material containing viruses.

Fortunately, although some bacteria can cause unpleasant or dangerous infections, the majority of the resident bacteria on our skin are friendly. Scientists are making very interesting discoveries about the lives of these organisms and the ways in which they affect us. Skin bacteria may help us in more ways than we realize.


This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2013 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on May 24, 2013:

Thank you so much, drbj! I appreciate your visits and kind comments a great deal.

drbj and sherry from south Florida on May 24, 2013:

Since the skin is our largest organ, it well deserves the comprehensive compendium of information you have provided, Alicia. Thanks for your enormous and fascinating research.

Linda Crampton (author) from British Columbia, Canada on May 16, 2013:

Thank you, RTalloni! I appreciate your comment.

RTalloni on May 16, 2013:

A very interesting look at bacteria on the skin and the various disorders related to it. Thanks for putting the information together for us in an easy-to-read format!

Linda Crampton (author) from British Columbia, Canada on May 16, 2013:

Thank you very much for the comment, Peggy. I appreciate the pin and the votes, too. I agree with you - washing the hands is a very important step for preventing disease!

Peggy Woods from Houston, Texas on May 16, 2013:

Well written and researched hub Alicia. I will be happy to pin this to my Health Related Subjects board on Pinterest. Also voting this up and useful. So glad that you stressed the importance of washing hands! It is one of the simplest ways to avoid getting ill.

Linda Crampton (author) from British Columbia, Canada on May 13, 2013:

Thank you very much for the vote and the share, starbright! I appreciate your visit and comment.

Linda Crampton (author) from British Columbia, Canada on May 13, 2013:

Hi, self-counsel. Thank you for the comment!

Lucy Jones from Scandinavia on May 13, 2013:

It's a bit creepy and a good thing we can't see everything that's going on with our bodies. Fantastic hub and very interesting despite the creepiness :-) Thanks for sharing. Voted and shared.

Linda Crampton (author) from British Columbia, Canada on May 11, 2013:

Thanks for the comment, Nell. I appreciate the vote and the share, too! It is very interesting that we have both good and bad bacteria sharing our body with us.

self-counsel on May 11, 2013:

Thanks for a very informative hub! Skin has a normal bacterial flora that serves useful purpose. Some of these organisms produce organic acids that prevent harmful organisms from accumulating.

Nell Rose from England on May 11, 2013:

Wow all those little bugs! seriously though its fascinating to know that we have good bacteria as well as the bad, and the bit about the mice was interesting too, to think that without their bacteria they were more suseptible to illness compared to the others, fascinating hub, and voted and shared, nell

Linda Crampton (author) from British Columbia, Canada on May 11, 2013:

Thanks, Deb. Yes, the bacteria on our skin are busy creatures! It's strange that so much is happening without us seeing it.

Deb Hirt from Stillwater, OK on May 11, 2013:

I didn't realize there was so much going on with bacteria in our daily lives. A great article.

Linda Crampton (author) from British Columbia, Canada on May 09, 2013:

Thank you very much for the vote and the share, Bill! Yes, bacteria are interesting creatures. Some are so helpful and some are so harmful!

Bill De Giulio from Massachusetts on May 09, 2013:

Great job Alicia. I think we all need an education about bacteria. With all of the anti-bacterial soaps, lotions, etc. out there people are convinced that all bacteria is bad for us. This was a great explanation of how bacteria works and what to watch for. Thanks for the education. Voted up, shared, etc....

Linda Crampton (author) from British Columbia, Canada on May 09, 2013:

Hi, Sue. Your experience in hospital sounds scary! Thanks for the comment and the votes.

Linda Crampton (author) from British Columbia, Canada on May 09, 2013:

Thank you for the comment, Tom. I appreciate the votes, too!

Susan Bailey from South Yorkshire, UK on May 09, 2013:

Voted up and interesting. Great hub. I was amazed when I was in hospital not long ago just how many of the nurses and doctors didn't wash their hands or use the antibac gel. No wonder there's MRSA running rife.

Thomas Silvia from Massachusetts on May 09, 2013:

Hi my friend, very interesting and well written and informative article with some useful information on these skin conditions . Well done !

Vote up and more !!!

Linda Crampton (author) from British Columbia, Canada on May 09, 2013:

Thank you very much for the comment, the vote and the share, gags3480!

GAGANPREET SINGH BHATIA from Kanpur, India on May 09, 2013:

Thanks for this useful info. You did a really good job.

Voted up & Shared.

Linda Crampton (author) from British Columbia, Canada on May 08, 2013:

Thank you very much for the comment, Bill!!

Bill Holland from Olympia, WA on May 08, 2013:

Wow! Great job of compiling information, Alicia. This is a treasure chest of knowledge and written very well.

Linda Crampton (author) from British Columbia, Canada on May 08, 2013:

Thank you very much for the comment and for passing the hub on, vocalcoach! I appreciate your visit.

Linda Crampton (author) from British Columbia, Canada on May 08, 2013:

Thank you very much, mnkk! I appreciate the comment.

Audrey Hunt from Pahrump NV on May 08, 2013:

Very useful information. I'm passing this on as we all need to read about bacteria on the skin. Thanks so much for writing this hub.

Kathleen March from Brunswick, Maine on May 08, 2013:

Very well written and with a perfect amount of information. I enjoy reading your health hubs!