The truth about zits | Science News for Students

The truth about zits

How germs help keep your skin healthy — or make it break out
Jan 22, 2016 — 7:00 am EST
clear skin

Scientists are working to understand the conditions that lead to clear skin versus breakouts of unsightly acne. And as breakouts are common, particularly among teens, research on new treatments is also underway.

Maria Morri/ Flickr (CC BY-SA 2.0)

Have you ever woken up in the morning only to feel a throbbing ache on the side of your nose? You wander into the bathroom, and — horror of horrors! — a huge red zit sprouted in the middle of the night. If you’re lucky, this doesn’t happen to you on school picture day or the night of a dance. But it could. At some point, pimples will erupt on the face of about 17 in every 20 people. This unpleasant skin condition, known as acne, plagues teens more than any other age group.

Acne hurts. And it can be embarrassing. But some lucky people never get zits — not even as teens. Rumors abound about what causes or prevents acne. Some people blame outbreaks on a diet too rich in dairy products or on sloppy personal hygiene. The truth, it turns out, is more complicated. While hygiene and diet may play some role in an outbreak, teens could cut out all milk and cheese and wash their faces twice a day and still break out.

milk and cookiesIn fact, washing too much can actually make acne worse, notes Rita Pichardo-Geisinger. She’s a dermatologist at Wake Forest Baptist Medical Center in Winston-Salem, N.C. Soap dries out your skin, and dry skin gets red and inflamed more easily.

So what triggers acne? Several factors make a difference. A person’s DNA — the genetic code that tells cells how to grow — can make some people more prone to acne. So can levels of hormones in the body and the particular bacteria that take up residence on the skin.

Scientists are particularly interested in one bacterium. It’s called Propionibacterium (PRO-pee-OH-nee-bak-TEER-ee-um) acnes, or P. acnes for short. It takes its name from where it thrives — inside pimples. This germ usually helps keep skin healthy. But it can have a disfiguring alter ego, sometimes making people break out. Researchers hope to someday develop treatments that use beneficial P. acnes bacteria to fight cousins that promote pimples. Other researchers are looking at new ways to heal acne using colored light.

A party in the pores

Vineet Mishra remembers getting a zit on his nose when he was a teen. “It was stressful,” he recalls. This dermatologist at UT Medicine, part of the University of Texas Health Science Center in San Antonio, has now seen plenty of cases far worse than his own. Some people experience outbreaks that blanket their entire face, neck, shoulders, chest or back.

Simply put, a pimple is an inflamed spot on the skin. It develops after a small opening in the skin, called a pore, becomes clogged with oil, bacteria, sweat, dirt or dead skin. The body doesn’t like having all that gross stuff stuck inside. So the immune system, which is responsible for fighting infections, may kick into action. In order to clear out damaged cells and start repairs, the immune system sends extra blood and chemicals to the problem area. Often, the area reddens and swells up. This is called inflammation, and it usually means that the body is working hard to repair itself.

But sometimes the body overreacts. This is especially likely if you pick at the sore spots. Picking at a pimple “will produce more inflammation, making the area redder, more painful and even more swollen,” says Mishra.

A clogged pore that hasn’t closed up completely forms a tiny pimple called a blackhead. A whitehead happens when the pore seals up and swells with inflammation. Some unlucky people also get large lumps or even oozing sores.

zitsTeens going through puberty get acne more often — and more severely — than anyone else. Blame hormones, those chemicals that are orchestrating the body changes that will transform a child into an adult. As puberty begins, the body boosts its production of several important sex hormones. Key among them are classes known as androgens and estrogens. These hormones trigger a host of changes. In boys, they can lead to the development of a lower, deeper voice, the emergence of an “Adam’s apple” and facial hair. In girls, they reshape the body, creating breasts and moving fat to the hips and thighs.

These hormones also tend to make glands in the skin boost their production of sebum. That bonus oil means there’s a higher chance that pores will clog. What’s more, the P. acnes germs love to eat sebum. So the more of this greasy substance that builds up on the skin and in the pores, the faster these germs  can grow. And that means there will be more germs around to colonize the pores, promoting zits.

Acne usually all but disappears in adulthood. By then, the body has cut back on levels of many hormones that had gone into overdrive during puberty. So the skin produces less sebum, which means fewer pores risk becoming clogged.

The bugs on your face

P. acnes can be found on everyone’s face — all the time. But don’t start madly trying to wipe or scratch these bacteria off! They are a normal part of a vast community of germs that live on skin. “We are not just humans. We are colonized by many, many bacteria,” explains Huiying Li, of the University of California in Los Angeles. As a microbiologist, she studies bacteria.

zit bacteriaScientists call a community of bacteria and other germs a microbiome (My-kroh-BY-oam). These communities dwell on all surfaces of the body — from the face and feet to the stomach and intestines. Each location hosts a different community of the freeloading microbes. “You can think about the microbiome the way you think about a lake or a forest,” says geneticist George Weinstock. “It has lots of different types of life in it.” Weinstock works at the Jackson Laboratory for Genomic Medicine in Farmington, Conn.

Some residents of a microbiome can make people very sick. Most instead coexist peaceably with their human hosts. In fact, many actually offer services to their hosts. Some help people digest food. Others produce chemicals that the body needs but cannot make.

P. Acnes usually helps break down sebum. As long as pores are open, this bacterium helps maintain a protective barrier over the skin’s surface. But when P. acnes gets trapped inside a clogged pore, these microbes can trigger painful inflammation.

Li, Weinstock, and colleagues suspected that people who are more prone to acne might host bigger populations of P. acnes. More microbes, they thought, might up the risk that some would settle down inside a clogged pore. To test this idea, the researchers recruited 49 acne patients and 52 people with healthy skin. They removed bacteria from the volunteers’ noses using sticky cleansing strips about the size of band-aids. To Li’s surprise, they found the same number of P. acnes in both groups.

Then, the researchers took a closer look at the different types, or strains, of P. acnes that they had retrieved. To do that, they used a technique known as ribotyping. Here, the researchers separated out a piece of DNA from the bacterial cell. Then they compared it to the DNA of other bacteria. With this method, the researchers turned up hundreds of different strains of P. acnes. They selected 10 of the most common strains, naming them RT1, RT2, RT3 and so on. “RT” stands for “ribotype.”

p. acnesThe strains’ genes differed ever so slightly. As a result, the bacteria also behaved somewhat differently. On human skin, the strains compete with one another. Each tries to inhabit as much skin as it can. The RT6 strain tends to live on healthy skin, Li’s team found. RT4 and RT5, on the other hand, show up mainly on skin with acne. Other strains show up equally on both types of skin.

Each strain has its own strategy for battling other bacteria. Sometimes, these conflicts lead to acne. The researchers don’t yet know exactly what weapons the strains bring to these battles. Weinstock speculates that strains RT4 and RT5 might produce chemicals that make the skin a less attractive home for other types of P. acnes. If those chemicals also cause nasty pimples, then they will make people’s faces less attractive, too!

Weinstock thinks RT6, the strain more often found on healthy skin, must use a different strategy that helps keep zits away. He doesn’t know what that strategy is yet, but one possibility is that RT6 might make a weapon that kills other P. acnes strains without damaging skin. Weinstock says uncovering RT6’s strategy and the role it plays in skin health might eventually help researchers develop new treatments for acne.

May the good guys win

Currently, doctors use several types of medications to treat acne. Over-the-counter skin cleansers (such as Clearasil or Stridex) can help a mild outbreak. These products use chemicals to bring down swelling and slow bacterial growth. A doctor also may prescribe a medicine called a retinoid ointment. It uses a Vitamin A-type substance to open up the pores so that other medicines can get in. Still other treatments focus on controlling inflammation.

teen with zitsAnother option is antibiotics. This type of medication kills P. acnes, which can help clear up an acne outbreak. However, antibiotics kill all bacteria — they don’t know the difference between “good” and “bad” strains. What’s more, over time some strains of bacteria change, or evolve, to resist antibiotic treatments. Then, the medicine will no longer work.

One promising alternative to antibiotics uses colored light, says Mishra. This approach, called photodynamic therapy, has become popular over the past decade. Researchers discovered that certain wavelengths of light would basically fry P. acnes bacteria. Ultraviolet light, a type of energetic light found in bright sunshine, works well to kill bacteria and clear up acne. But exposure to these powerful beams can damage the skin or even cause cancer. Blue-colored light is less energetic and safer. Yet it still destroys P. acnes bacteria.

Some dermatologists instead use lasers to target oil glands in an area of the skin that is prone to acne outbreaks. The laser light destroys some of the glands. This leads to a drop in sebum production, making acne outbreaks less likely to begin or worsen.  

Some experimental acne medications introduce helpful bacteria to fight off harmful ones. This type of drug is known as a probiotic (PRO-by-OT-ik). Dermatologists are still working to develop and test probiotic treatments for acne. In one 2013 study, researchers at the University of Alberta in Edmonton looked at the effects of probiotics. They divided 45 acne-afflicted volunteers into three groups. One group received only an antibiotic, the second group only a probiotic, and the third group received both. After 12 weeks, everyone’s acne had improved. But the group that received both treatments had the clearest skin.

Future probiotics for acne could put good strains of P. acnes to work, Weinstock imagines. Teens might one day fight zits by transferring a strain such as RT6, from one part of the body to another. “Wouldn’t it be great,” he says, “if you could take some kind of adhesive tape, put it down on normal skin and pull it up, then put it on the acne and keep it there while you go to sleep?” The good bacteria would compete with any bad ones, and hopefully the good guys would win.

Teens using this approach could sleep while microbial battles raged on their faces beneath the adhesive tape. Good bacteria from healthy skin would fight for control of the pimply area. By morning, the good bacteria would have taken over. The tape could now come off, and the zits would gradually disappear. If it sounds too good to be true, it is — today. But a treatment like this might be on the horizon, thanks to the tiny bugs that call your face home. 



Word Find (click here to enlarge for printing)

Power Words

(for more about Power Words, click here)

acne    A skin condition that results in red, inflamed skin, commonly called pimples or zits.

antibiotic  A germ-killing substance prescribed as a medicine (or sometimes as a feed additive to promote the growth of livestock). It does not work against viruses.

bacterium (plural bacteria)  A single-celled organism. These dwell nearly everywhere on Earth, from the bottom of the sea to inside animals and humans.

blackhead    A type of pimple that forms when oil, dead skin and bacteria build up near the top of an open skin pore, pushing it open. Oxygen in the air causes the oil clogging the pore to blacken.

dermatology  The branch of medicine concerned with skin disorders and their treatments. Doctors who treat these disorders are called dermatologists.

evolve  (adj. evolving)  To change gradually over generations, or a long period of time. In living organisms, the evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).

gene  (adj. genetic) A segment of DNA that codes, or holds instructions, for producing a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

gland  A cell, a group of cells or an organ that produces and discharges a substance (or “secretion”) for use elsewhere in the body or in a body cavity, or for elimination from the body.

hormone   (in zoology and medicine)  A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

immune system  The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

inflammation The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It is also an underlying feature responsible for the development and aggravation of many diseases, including acne.

microbe   Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microbiology   The study of microorganisms, principally bacteria, fungi and viruses. Scientists who study microbes and the infections they can cause or ways that they can interact with their environment are known as microbiologists.

microbiome   The group of microorganisms living in a particular place.

photodynamic therapy    A treatment for skin conditions including cancer or acne. The treatment uses laser light of a particular wavelength to activate a chemical product applied to the skin.  

pore    A tiny hole in a surface. On the skin, substances such as oil, water and sweat pass through these openings.

probiotic   A material that serves as food or otherwise encourages the growth of good bacteria in some area of the body.

Propionibacterium acnes (or P. acnes)    A species of bacteria that takes its name from where it thrives — inside pimples. Ironically, this germ usually helps keep skin healthy.

puberty   A developmental period in humans and other primates when the body undergoes hormonal changes that will result in the maturation of reproductive organs.

retinoids    Any of a series of chemicals that are related to Vitamin A. Retinoid ointments help treat acne.

ribotyping    A technique that allows researchers to identify different strains of bacteria. The process involves cuttingout a piece of bacterial DNA and analyzing it in order to compare it to the DNA of other bacteria.

sebum   A type of oil secreted by glands (sebaceous glands) in the skin. It helps keep the skin moist and healthy.

strain  (in biology) Organisms that belong to the same species that share some small but definable characteristics. For example, biologists breed certain strains of mice that may have a particular susceptibility to disease. Certain bacteria or viruses may develop one or more mutations that turn them into a strain that is immune to the ordinarily lethal effect of one or more drugs.

whitehead   A type of pimple that forms when oil, dead skin and bacteria block a skin pore completely.

zits   A colloquial term for the pimples caused by acne.


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Further Reading

S. Ornes. “The power of microbes.” Science News for Students. July 11, 2013.

Learn more about acne from the National Institutes of Health.

Learn more about ribotyping from Cornell University.

Questions for "The truth about zits"