Helping People Achieve Clear Skin Since 2007

Helping People Achieve Clear Skin Since 2007

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What Causes Acne? Everything You Need to Know

By Dr. Jaggi Rao, MD, FRCPC, Double board-certified dermatologist

There is no single answer to the question of what causes acne because acne is a multifactorial condition, meaning it is caused by multiple factors interacting with each other. It’s true that having oily skin can increase your likelihood of having acne, but it’s also true that people with dry skin can be especially acne-prone as well. How exactly does this work? Throughout this article, we’ll explore the ins and outs of how acne forms so that you are better equipped to treat and prevent it.

Once you find out what’s causing your acne, you’ll be on the road to clearer, healthier skin.


  • Acne is caused by both primary factors, like inflammation and bacteria, and secondary factors, like diet and genetics.
  • Acne is an inflammatory condition, meaning all acne starts with some degree of inflammation.
  • The oil our skin naturally produces to protect itself, called sebum, can lead to clogged pores and increased bacteria when it is overproduced.
  • Acne-causing bacteria always live on our skin and only cause a problem when they start multiplying too rapidly.
  • Hormonal shifts, such as those experienced during puberty, before menstruation, or during pregnancy, may cause changes to your sebum that result in more acne.
  • Studies have found that genetics play a large role in who develops acne and who maintains clear skin.
  • There is an increasingly strong link between stress and acne, especially when it comes to long-term, chronic stress.

Primary vs. Secondary Causes of Acne

The causes of acne essentially break down to three basic issues: inflammation, sebum, and bacteria. If you know your stress levels or diet have an effect on your acne, you may be wondering where those factors fit into this picture. Well, those factors and others like them are actually considered secondary causes of acne. Genetics, hormones, and sensitive skin can all cause acne, but they do so by affecting the three basic, or primary, causes of acne: inflammation, sebum, or bacteria.

It’s important to understand how the primary factors affect your acne directly because it can help you understand which secondary factors are really causing a problem for you. For instance, we don’t have much hard evidence that diet affects acne, but that isn’t because it doesn’t. It’s just that diet studies are very difficult to conduct and getting conclusive results takes time and lots of repeated experiments. But if you understand how food relates to inflammation, and how inflammation relates to acne, you may be able to weed out foods that may be a secondary cause of your acne.

Primary Cause #1: Inflammation

Acne is first and foremost an inflammatory condition, meaning that all acne starts with some degree of inflammation. Because the primary causes of acne are all connected, reducing inflammation won’t get rid of your acne entirely, but it can definitely help.

No matter what kind of acne you have, from the smallest blackheads to the deepest cysts, all acne starts when the skin becomes inflamed. Inflammation causes the skin to swell slightly, which leads the pores to constrict, which is why it’s a problem for acne. When the pores constrict, any dead skin cells, sebum, and bacteria that were inside get trapped, where they can form a variety of acne-related problems. If it’s just dead skin cells and sebum (the oil our skin naturally produces to protect itself) then a blackhead or whitehead forms. If bacteria are also trapped, then a pimple or cyst typically forms. Without this initial inflammation, it is much harder for the other two primary causes of acne, sebum and bacteria, to take hold and actually cause much acne. However, the kind of minor inflammation that causes our pores to constrict occurs every day, multiple times a day. Unfortunately, we aren’t able to avoid it entirely. However, there are ways to decrease it.

First, be sure to include a moisturizer in your daily acne skin care routine. Many people with acne avoid moisturizers for fear of clogging their pores, but in reality, moisturizer helps prevent inflammation and thus helps prevent acne. Second, try to avoid picking or scratching at your acne, as this tends to inflame the skin as well. Finally, you can avoid acne-causing inflammation by looking for skin care products and foods containing antioxidants. Check out our section on acne and diet for more information on what antioxidants can do for acne.

Reducing inflammation with antioxidants like those found in blueberries is one of the best ways to help reduce acne.

Primary Cause #2: Sebum

Sebum is the scientific name for the waxy, oily substance our skin creates in order to protect itself. When produced correctly, it is vital for healthy skin, but if our skin produces too much or too little, acne is sure to ensue.

Done right, sebum helps prevent inflammation by preventing irritation. Minor physical irritations like scratchy fabric or a harsh winter wind can damage our skin cells on the microscopic level, and our bodies heal this damage through the inflammation response, which we now know can lead to increased acne. However, a fine layer of sebum can protect our skin from these everyday irritants, thus preventing the inflammation and potentially preventing some acne.

This is the main reason that dry skin often have acne-prone skin. People with dry skin do not produce enough sebum to protect their skin, and even the smallest irritants can cause damage, inflammation, and acne. Still, too much sebum can be a bad thing as well. According to a study published in the Journal of European Academy of Dermatology and Venereology, increased sebum production is associated with increased acne formation. When too much sebum is produced, it gets backed up in the pore, causing a clog which often results in the formation of a blackhead. Excess sebum also provides extra food to acne-causing bacteria, which consume our sebum as their main food source. With all that extra food, they can multiply at even faster rates, leading to minor infections which turn into pimples or cysts (more information in our next section on acne-causing bacteria).

To get rid of excess sebum, we recommend mild chemical exfoliation with ingredients like salicylic acid, azelaic acid, or glycolic acid. If you have dry skin and aren’t producing enough sebum, we recommend a good moisturizer containing protective (but non-pore-clogging) ingredients like petrolatum or beeswax.

Primary Cause #3: Bacteria

The bacteria most closely associated with acne are known as Propionibacterium acnes, or p. acnes for short, and even though they can cause acne, they aren’t all bad. P. acnes actually always live on the surface of our skin, whether we have acne or not, meaning they don’t automatically cause acne. P. acnes only cause a problem when one of the other primary causes of acne flares up. For instance, p. acnes can become a problem if we start overproducing sebum and they have an overabundance of food, or if our skin becomes inflamed and the pores constrict, trapping p. acnes inside.

In both of these instances, the p acnes are given a chance to multiply even faster than normal until their numbers are large enough to create an infection. Once the immune system realizes there’s an infection, it triggers more inflammation to increase blood flow to the site of the infection and to prevent the bacteria from spreading. Immune system cells arrive, fight the p. acnes, and often die themselves in the process. The resulting dead cell matter forms the pus that gives pimples, cysts, and nodules their yellow-ish color.

In the past, dermatologists used to prescribe antibiotics for people whose acne was mostly made up of pimples or cysts, but today we know that antibiotic resistance is on the rise, and other options need to be explored. One of the most popular option for killing p. acnes and getting rid of pimples is benzoyl peroxide. Benzoyl peroxide is skin care ingredient found in face creams, gels, and washes, and it works by bringing extra oxygen below the surface of the skin. P. acnes bacteria are anaerobic, meaning they can’t survive long in the presence of oxygen. This allows benzoyl peroxide to kill p. acnes bacteria without increasing antibiotic resistance.

Top-Rated Acne Treatment Products

The best acne treatment products are ones that include ingredients that will directly affect the primary causes of acne. Treatments that address the secondary causes may work for some, but if you want to get directly to the heart of the issue, it’s best to find products that kill bacteria, reduce inflammation, and/or control sebum. Below we’ve listed three of our favorite acne treatment products that do exactly that.

Exposed Skincare product with rose petals on white background.
Exposed Skin Care is one acne treatment company that can help just about anyone reduce their acne, no matter what their genes have to say about it.

Exposed Skin Care: We recommend Exposed Skin Care products because its clear from their ingredient lists that the creators did their research and truly understand what causes acne. Their products contain benzoyl peroxide and tea tree oil kill p. acnes bacteria, salicylic acid and glycolic acid exfoliate the skin and help remove excess sebum, and green tea extract and aloe vera soothe the skin and reduce inflammation.

Cetaphil PRO DermaControl: Cetaphil’s new DermaControl line contains zinc and glycerin, which both help protect the skin and reduce inflammation, plus PEG-200 Hydrogenated Glyceryl Palmate, which sounds like a bad, scary chemical, but is really just a gentle surfactant that can help remove oil without irritating the skin.

Aveeno Clear Complexion: All of Aveeno’s Clear Complexion products contain salicylic acid, a great ingredient for exfoliating the skin to remove excess sebum. Many of their products also contain citric acid, another great exfoliator, and glycerin, to help protect the skin from irritation.

Secondary Causes of Acne

All acne is caused by some combination of the above three factors, no matter what the secondary cause is. There are thousands of secondary causes for acne, but we’re going to discuss the top five: diet, hormones, chronic stress, genetics, and other health conditions that can potentially affect acne. like polycystic ovarian syndrome.

Diet and Acne: Is There a Connection?

So far, scientists haven’t found a conclusive connection between diet and acne, but that probably has more to do with the complex nature of diet studies than it has to do with the relationship between the two. There are a lot of complications that can arise with diet studies, from dishonest participants to uncontrollable variables.

However, we do have some conclusive information about food and inflammation, and based on what we know about inflammation and acne, we can use this information to better understand how diet and acne might be related. However, before we get started, we want to make one thing very clear: going on any kind of extreme diet will not help your acne, or your mental health. Studies show that the stress of restrictive diets significantly worsens health, and it is far better to focus on moderation rather than cutting a food out entirely.

When adjusting your diet to help reduce acne, it’s important to avoid harsh restrictions, as they tend to only make health worse.

Diet and Acne: Antioxidants

That’s why we want to start with a food group you’ll actually want to increase: antioxidants. Antioxidants function by helping to reduce oxidative stress, which is a phenomenon in which oxygen molecules lose an electron. The oxygen molecule becomes aggressive and volatile in its search for a new electron, often causing cell damage in the process. This damage leads to increased inflammation throughout the body, including in the skin.

Antioxidants help prevent this damage by providing these volatile oxygen molecules with a spare electron. This makes antioxidants a strong potential treatment for acne because inflammation is at the heart of all acne lesions, and when inflammation decreases, acne in general also tends to decrease. Studies have found that antioxidant-rich vitamins and minerals like vitamin E and zinc are more likely to significantly reduce acne compared to a placebo.

Antioxidants can be found in all kinds of foods, from berries to beans to apples, even chocolate. However, we wouldn’t go out and buy a case of “acne-fighting” chocolate just yet. Chocolate contains many ingredients that may be linked to increased acne, like sugar, dairy, and caffeine, and according to a study published in the Journal of the American Academy of Dermatology, daily chocolate consumption led to a significant increase in acne.

Diet and Acne: Glycemic Load

Although the chocolate study fell prey to the traps inherent in all diet studies, we are inclined to believe that consuming chocolate every day really might lead to an increase in acne. Chocolate could be problematic for your skin because of how quickly our bodies break down and absorb its sugar.

When it comes to sugar in your food, there are two numbers you should know: its glycemic index and its glycemic load. The glycemic index is a number from 1 to 100 that ranks how much sugar the food contains. You might be tempted to think that this number was the one that mattered. But the truth is, the glycemic load is the far more important number since several studies have found that glycemic load and acne are correlated.

A food’s glycemic load is an indication of not only how much sugar the food contains, but also how quickly our body absorbs it. Large amounts of sugar actually aren’t a bad thing for the skin as long as that sugar is delivered to the bloodstream slowly and steadily. For instance, a watermelon has a glycemic index of 72, which is very high, but its glycemic load is only 2. The sugars in a watermelon are broken down slowly and so it doesn’t cause any large spike in blood sugar. Pancakes, on the other hand, have a glycemic index of 67, lower than watermelon, but a glycemic load of 39, much higher than watermelon. The sugar in pancakes arrives in our bloodstream very quickly, causing a large spike in blood sugar.

So why is this a problem for acne? Simple: large amounts of sugar in our blood are more difficult to break down, and to deal with these spikes, our bodies produce extra hormones which then cause an increase in acne.

Hormones and Acne

Hormones play a pivotal role in acne because they directly affect the sebum we produce. Our bodies produce thousands of hormones in very specific amounts all day every day, in a highly individualized, intricate system. Because of this, it is impossible to say that any one particular hormone “causes” acne. Instead, we have found that hormonal changes and fluctuations are responsible. Specifically, most studies are able to trace changes in acne back to changes in androgen levels, like testosterone.

Even though testosterone is known as a classically “male” hormone, everyone, regardless of sex or gender, produces both testosterone and estrogen (the classically “female” hormone). Men and some intersex folks tend to produce more testosterone while women and other intersex folks usually produce more estrogen. Whatever amount of these hormones you produce naturally should not cause acne, unless you have a hormonal condition like the one we will discuss further on in this article. Hormones cause problems for acne only when they fluctuate and deviate from their typical baseline production amounts. Unfortunately, this happens a lot.

Some key populations often affected by hormonal acne include teenagers going through puberty, people experiencing menstruation, pregnancy, or menopause, people using anabolic steroids, or trans men undergoing testosterone therapy. In all of these cases, testosterone levels increase above what your body typically naturally produces, and as a result, the sebaceous glands go into overdrive and produce more sebum than you really need. This excess sebum has been linked to increased cystic and nodular acne, and many researchers believe it is also linked to more mild and moderate acne.

Chronic Stress and Acne

The hormones most commonly associated with acne are sex hormones like testosterone, but if you suffer from chronic stress, then stress hormones like cortisol and adrenaline could also be contributing to your acne.

Chronic stress can contribute to acne, so stress-relieving activities like baking, coloring, or therapy may be a helpful way to reduce your acne as well.

The stress response is our body’s way of trying to protect us, though it is rather misguided. Whenever we’re faced with a personal, emotional, or occupational stressor, our body reacts as if it is a physical threat, with the fight, flight, or freeze response. If we really were facing a physical threat, the fight, flight, or freeze response is a great way to protect ourselves, but when facing a non-physical stressor, this response is the reason we may feel anxious, restless, or trapped, and it can have physical repercussions as well.

When we experience the fight, flight, or freeze response, our body releases a boost of cortisol. If this only happens every now and again, the extra cortisol can help prevent inflammation to keep our body in better shape for a fight. However, if we are chronically stressed and cortisol boosts are released regularly, inflammation can actually increase as our body becomes immune to the constant influx of cortisol.

According to the Mayo Clinic, this increase in overall inflammation can have consequences for our health in many areas, but it can also affect our acne. With more inflammation comes more acne, which is why you may notice increased breakouts around finals week or just days before a big presentation.

Genetics and Acne

One of the most powerful influences over a person’s acne is their genetics. Someone might wash their face with the perfect face wash, eat plenty of antioxidants, and keep their stress at a minimum, and still get consistent breakouts, while someone else might do nothing at all to help their skin and never get a single pimple. It’s unfair, but that’s just how genetics works.

Our genes determine a lot about our life, from our eye color to the likelihood we will get divorced, so it should be no surprise that they also have an impact on our acne. Children of parents with acne are significantly more likely to develop acne at some point in their life, and according to a twin study published in Twin Research and Human Genetics: The Official Journal of the International Society of Twin Studies, monozygotic twins (identical twins) are more likely to have the same acne status than dizygotic twins (fraternal twins). This strongly indicates that genes play a major role in whether or not someone has acne.

They haven’t yet discovered exactly which genes are related to acne, but it’s likely that certain genes related to skin cell production, sebum production, and the immune system (and thus the inflammation response) are involved.

Polycystic Ovarian Syndrome and Acne

Although acne itself is a relatively harmless, albeit very frustrating, condition, in some cases it can be indicative of other problems that are not so harmless. The biggest example of this is acne and PCOS, or Polycystic Ovarian Syndrome.

PCOS is an under-researched, poorly understood hormonal condition that most commonly occurs in women. It causes a wide variety of symptoms, from ovarian cysts to excess hair growth to unpredictable weight gain, and of course, acne, though no two cases of PCOS look alike. In fact, although cysts are in the name, a large percentage of people with the condition never experience an ovarian cyst. Not everyone with PCOS has acne, and not everyone with acne has PCOS, but according to a study published in the European Journal of Obstetrics, Gynecology, and Reproductive Biology, women with disorders that affect their androgen levels (like PCOS) are far more likely to get acne than women without such disorders.

Because PCOS research is only now getting some real traction, it is still widely underdiagnosed. If you notice that your acne is very closely linked to hormonal shifts or to your diet, and you also notice some of the other common symptoms of PCOS, we encourage you to seek out a doctor who is known for their knowledge of PCOS. Many doctors are still undereducated on the topic and may miss important red flags, so it’s important to see someone who has good reviews from other PCOS patients.

What Comes Next?

Once you have a better grasp on what’s causing your acne, it’s time to take the next, and most exciting, step: treatment. We have a variety of articles on different acne treatments, from the best home remedies for acne, to the best acne prescriptions, and a page comparing some of the top acne products on the market today. Feel free to peruse and find the solution to your acne today.

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