Understanding Acne

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Acne comes in many shapes and forms, and knowing how to identify the different types of acne can help you better understand how to treat them. In this post, we’ll review the different types of acne that can appear on your face and review various treatment options.

Fast facts on Acne

Here are some facts about acne. More detail is in the main article.

  • Acne is a skin disease involving the oil glands at the base of hair follicles.
  • It affects 3 in every 4 people aged 11 to 30 years.
  • It is not dangerous, but it can leave skin scars.
  • Treatment depends on how severe and persistent it is.
  • Risk factors include genetics, the menstrual cycle, anxiety and stress, hot and humid climates, using oil-based makeup, and squeezing pimples.

What is acne?

Acne is a skin condition that occurs when your skin pores are blocked by oil, bacteria, dead skin cells, and/or dirt. The oil glands under our skin release sebum (oil), which normally travels up the oil glands and onto the surface of our skin, keeping our skin soft. However, a build-up of oil, bacteria, or dead skin cells trapped in our pores can lead to inflammation. Acne is a physical manifestation of this inflammation.

A common mistake people make is confusing acne with fungal acne because they can look similar. While the two can have a similar appearance, there are distinct differences when it comes to causes and treatments.

What causes acne?

The exact causes of acne still remain unclear, but there is proof that a few factors affect the presence or severity of acne. 

Acne is caused when tiny holes in the skin, known as hair follicles, become blocked.

Sebaceous glands are tiny glands found near the surface of your skin. The glands are attached to hair follicles, which are small holes in your skin that an individual hair grows out of.

Sebaceous glands lubricate the hair and the skin to stop it from drying out. They do this by producing an oily substance called sebum.

In acne, the glands begin to produce too much sebum. The excess sebum mixes with dead skin cells and both substances form a plug in the follicle.

If the plugged follicle is close to the surface of the skin, it bulges outwards, creating a whitehead. Alternatively, the plugged follicle can be open to the skin, creating a blackhead.

Normally harmless bacteria that live on the skin can then contaminate and infect the plugged follicles, causing papules, pustules, nodules or cysts.

Why does acne eventually clear up?

We do not understand why acne eventually clears up. It does not always coincide with a reduction in sebum production or with a reduction in the number of bacteria. It may relate to changes in the sebaceous glands themselves or to the activity of the immune system.

Nutrition and diet

First, nutrition and diet play a role in inflammation in our bodies and, in turn, acne. Studies show that certain foods high in sugar and dairy can raise hormone levels (IGF-1), which leads to an overproduction of sebum and contributes to acne formation. 

Build-up of dead skin cells

Second, a build-up of dead skin cells can contribute to acne. The skin’s most outer layer, the epidermis, undergoes constant renewal. It naturally sheds skin cells as new ones generate every 28 days. When the dead skin cells stay and build up over time, they contribute to a clogged pore and potentially, a pimple. 


Teenage acne is thought to be triggered by increased levels of a hormone called testosterone, which occurs during puberty. The hormone plays an important role in stimulating the growth and development of the penis and testicles in boys and maintaining muscle and bone strength in girls.

The sebaceous glands are particularly sensitive to hormones. It’s thought that increased levels of testosterone cause the glands to produce much more sebum than the skin needs.

Runs in the family

Acne can run in families. If your parents had acne, it’s likely that you’ll also develop it.

One study has found that if both your parents had acne, you’re more likely to get more severe acne at an early age. It also found that if one or both of your parents had adult acne, you’re more likely to get adult acne too.

Acne in women

Women are more likely to have adult acne than men. It’s thought that many cases of adult acne are caused by the changes in hormone levels that many women have at certain times.

These times include:

  • periods – some women have a flare-up of acne just before their period
  • pregnancy – many women have symptoms of acne at this time, usually during the first 3 months of their pregnancy
  • polycystic ovary syndrome – a common condition that can cause acne, weight gain and the formation of small cysts inside the ovary

Overproduction of sebum

Lastly, an overproduction of sebum from our oil glands can contribute to acne. For example, using harsh products strips the natural oils from the surface of our skin, making it feel dry and overly taut. As a result, the oil glands respond by overproducing oil to try and compensate. Compounded over time, this can result in clogged pores and inflammation, which manifests in acne. 

Teen Acne

The precise reasons that acne is most severe during the teenage years are being studied. There are several theories.

There are higher levels of sex hormones after puberty than in younger children.

  • Sex hormones are converted in the skin to dihydrotestosterone (DHT), which stimulates sebaceous (oil) glands at the base of hair follicles to enlarge.
  • The sebaceous glands produce sebum. Changes in sebum composition may lead to acne lesions.
  • The activated sebaceous gland cells (sebocytes) also produce pro-inflammatory factors, including lipid peroxides, cytokines, peptidases and neuropeptides.
  • Hair follicles are tiny canals that open into skin pores (tiny holes) on the skin surface. The follicles normally carry sebum and keratin (scale) from dead skin cells to the surface. Inflammation and debris leads to blockage of the skin pores — forming comedones.
  • The wall of the follicle may then rupture, increasing an inflammatory response.
  • Bacteria within the hair follicle may enhance inflammatory lesions.

While acne is most common in adolescents, acne can affect people of all ages and all races. It usually becomes less of a problem after the age of 25 years, although about 15% of women and 5% of men continue to have acne as adults. It may also start in adult life.

Stress and acne

Stress causes a chemical response in your body that makes skin more sensitive and reactive. It can also make it harder for skin problems to heal.

Have you ever noticed that you break out more when you’re stressed? This is because stress causes your body to make hormones like cortisol, which tells glands in your skin to make more oil. Oily skin is more prone to acne and other skin problems.

Stress can also:

Make skin problems worse. For example, stress can aggravate psoriasis, rosacea, and eczema. It can also cause hives and other types of skin rashes and trigger a flare-up of fever blisters.

Interfere with daily skin care. If you’re stressed, you might skimp on this part of your routine, which can aggravate skin issues.

It can also be stressful to have problems with your skin. Some people feel so bad about how it looks that they keep to themselves, which adds more stress.

Most of us have had or at least known someone who’s had acne. About 85 percent of us will have some form of acne during our lives. For some, it may just be one or two bumps or pimples, but for others, it can be extreme and lead to scarring.

Acne usually appears on your face, back, or even your neck and shoulders. Although it occurs most often during the teenage years, it can affect you at any age.

The relationship between stress and acne has been misunderstood by many. Stress can’t directly cause acne. However, if you already have acne, stress does make it worse.

Researchers have found that wounds, including acne, are much slower in healing when a person is under stress. Slower healing of acne means that the pimples stay longer and are more susceptible to increase in severity. It can also mean that more acne is visible at one time because it takes longer for each pimple to heal during a breakout.

Medical vector illustration of different types of acne on human skin. Appearance of pimples in hair follicle.

Why is acne worse in some people?

Some people have particularly severe acne. This may be because of:

  • Genetic factors (family members have bad acne)
  • Hormonal factors (higher levels of male/androgenic hormones) due to:
    • Polycystic ovaries (common). Hyperinsulinaemia and insulin resistance are characteristically found in women with polycystic ovarian syndrome, who are prone to acne among other problems
    • Psychological stress and depression
    • Excessive corticosteroids eg Cushing disease (rare)
    • Enzyme deficiency eg sterol hydroxylase deficiency (very rare)
  • Environmental factors such as:
    • High humidity causing swelling of the skin
    • Cosmetics especially certain moisturisers, foundation and pomades. Watch out for products that contain lanolin, petrolatum, vegetable oils, butyl stearate, lauryl alcohol and oleic acid.
    • Pressure from headbands and chin straps (eg “fiddler’s neck”, a condition seen in violin or viola players, where continual pressure from the violin against the neck causes skin irritation)
    • Excessive dairy products, meat protein and sugars in the diet. Diets low in zinc or high in iodine can worsen pustular acne.
  • Certain medications may provoke acne.
  • Much of the individual variation in acne severity is due to variation in the innate immune system and the production of inflammatory mediators such as cytokines, defensins, peptidases, sebum lipids, and neuropeptides. Evidence has emerged that inflammation leads to distension and occlusion of the hair follicle, which then ruptures.

The 6 Types of Acne


Whiteheads are a form of clogged pores that are characterized by small, white pus-filled blemish at the surface of the skin. Also known as closed comedones, they are caused by hair follicles clogged with oil. As seen in the above picture, whiteheads look like small, white bumps and are not sensitive to touch.

What do whiteheads look like? Small, white bumps that have a white or yellow fluid in the center.

In almost all cases, acne happens because the pores in your skin are clogged. Clogged pores can happen when there is too much oil, bacteria, or skin cell production, or as a result of hormonal changes. 

Whiteheads, also known as closed comedones, happen when pores are clogged all the way through. The length of the pore and the head of the pore are closed, creating a little white bump on top of the skin. It’s important to note that whiteheads can’t be removed or fixed by squeezing them, so don’t try to pop them on your own. Otherwise, you may end up with scarring.


Also called open comedones, blackheads are similar to whiteheads in that they are a result of clogged hair follicles and live at the surface of the skin. However, unlike whiteheads, they are exposed to oxygen in the air and go through an oxidation process that darkens their appearance. As a result, blackheads look like small, black dots, often in groups and smaller in size than whiteheads. 

What do blackheads look like? Small, black dots that are grouped together on the face, similar to freckles.

Unlike whiteheads, blackheads look black on the skin’s surface. They are known as open comedones because the head of the pore remains open, while the rest of the pore is clogged. Blackheads can be removed by squeezing, although that’s not recommended because it can cause scarring. 

Treatment options for blackheads are the same as treatments for whiteheads. Try to avoid using pore strips to pull out blackheads. Pore strips are an abrasive, temporary fix that can damage the top layer of your skin, making acne worse.


Papules are a more severe form of acne that occurs when whiteheads or blackheads become inflamed and infected. White blood cells rush to the infected area to treat the infection, which causes irritation to the infected area. 

What do papules look like? Red or pink raised bumps that are inflamed and sensitive to touch.

Papules are small red bumps that form when oil or excess skin cells block a pore and mix with bacteria on your skin called Cutibacterium acnes or C. acnes (formerly Propionibacterium acnes). The contents of this blocked pore spill out, which allows the bacteria to escape into the surrounding skin tissue. The bacteria then create an inflamed lesion. Papules do not contain pus.


If you’ve ever been tempted to “pop” a pimple that looks ripe for your picking, you’ve come across pustules. Pustules are also a more severe version of closed comedones; they often look like whiteheads, but bigger and more inflamed. The pus or fluid is much more visible to the eye and the affected area is larger than that of a typical whitehead.

What do pustules look like? Pustules look like pink or red raised bumps with a clear white or yellow pus-filled center.

Pustules are small, bulging bumps with a white centre and red, inflamed skin surrounding them. They are usually found in clusters on the chest, face, or back. Pustules form when a blocked pore gets infected, but they can also be caused by hormonal changes in the body. They are similar to papules, except pustules contain a yellowish fluid known as pus. 

Popping pustules may cause the bacteria to spread, so don’t try to pop or squeeze them. Only your doctor can safely drain pustules.


A nodule is a solid dome-shaped lesion that extends below the surface, deep into the layers of the skin. They are large, painful bumps that are harder than cysts and are not filled with pus. 

Nodular acne consists of flesh-coloured or red bumps that are deep under the skin’s surface. Nodular acne is usually a result of the C. acnes bacteria causing a painful infection deep within the pore.


Cysts form deeper within the skin surface and are indicative of inflammation and infection under the epidermis, the top layer of the skin. They are often bigger than papules or pustules, appear lighter in the middle where the pus accumulates, and are more painful to touch.

What do cysts look like? Cysts look similar to boils, with a larger bump deep under the skin’s surface.

Cystic acne is the most severe form of acne and is also the result of an infection deep within the skin. Acne cysts are large, red, inflamed, painful, and pus-filled. Cysts are softer than nodules because they are pus-filled and often burst, infecting the surrounding skin. 

What Is Rosacea?

If your face looks like you’re blushing and you get bumps that are a bit like acne, you might have a skin condition called rosacea. Your doctor can suggest medicine and other treatments to manage your symptoms, and there are plenty of steps you can take at home to make yourself look and feel better.


The biggest thing you’ll notice is redness on your cheeks, nose, chin, and forehead. Less often, the color can appear on your neck, head, ears, or chest.

After a while, broken blood vessels might show through your skin, which can thicken and swell up. Up to half of people with rosacea also get eye problems like redness, swelling, and pain.

Other symptoms you may get are:

  • Stinging and burning of your skin
  • Patches of rough, dry skin
  • A swollen, bulb-shaped nose
  • Larger pores
  • Broken blood vessels on your eyelids
  • Bumps on your eyelids
  • Problems with seeing

Your rosacea symptoms can come and go. They might flare up for a few weeks, fade, and then come back.

Getting treatment is a must, so make sure you see your doctor. If you don’t take care of your rosacea, redness and swelling can get worse and might become permanent.

What Causes It?

Doctors don’t know exactly what causes rosacea. A few things that may play a role are:

Your genes. Rosacea often runs in families.

Blood vessel trouble. The redness on your skin might be due to problems with blood vessels in your face. Sun damage could cause them to get wider, which makes it easier for other people to see them.

Mites. They’re tiny insects. A type called Demodex folliculorum normally lives on your skin and usually isn’t harmful. Some people, though, have a heightened sensitivity to the mites, or more of these bugs than usual.. Too many mites could irritate your skin.

Bacteria. A type called H. pylori normally lives in your gut. Some studies suggest this germ can raise the amount of a digestive hormone called gastrin, which might cause your skin to look flushed.

Some things about you may make you more likely to get rosacea. For instance, your chances of getting the skin condition go up if you:

  • Have light skin, blonde hair, and blue eyes
  • Are between ages 30 and 50
  • Are a woman
  • Have family members with rosacea
  • Had severe acne
  • Smoke

Food and Acne

Some studies suggest there is a link between the food we eat and acne. It is very difficult to study the role of diet and acne. 

Acne is reported to be less common in people that have a diet with a lower glycaemic index, eg, indigenous people from Kitava and Papua New Guinea, the Ache people of Paraguay, Inuit, and rural residents of Kenya, Zambia and Bantu. These people tend to become sexually mature at a later age than in the cities where higher glycaemic index foods are consumed. Early puberty is associated with earlier onset and more severe acne that tends to peak at the time of full maturity (age 16 to 18).

Several studies, criticised for their quality, have shown benefits in acne from a low-glycaemic, low-protein, low-fat and low-dairy diet. The reasons for these benefits are thought to relate to the effects of these foods on insulin and insulin-like growth factor-1 (IGF-1).

Insulin induces male hormones (androgens), glucocorticoids and growth factors. These provoke keratinisation (scaling) of the hair follicle and sebum production. An increase in sebum production and keratinisation is a factor in the appearance of acne.

On the other hand, a large prevalence study of acne in military recruits showed a lower prevalence in severely obese adolescents than in those of normal weight.

Foods that increase insulin production

Foods that increase insulin levels have a high glycaemic index. The glycaemic index is a measurement of how carbohydrates have an effect on our blood sugar levels. When we eat foods with a high glycaemic index, such as white bread and baked goods, our blood sugar level rises. This increases the amount of insulin produced in our bodies.

Although cow’s milk has a low glycaemic index, it contains androgens, oestrogen, progesterone and glucocorticoids, which also provoke keratinisation and sebum production. Milk also contains amino acids (eg arginine, leucine, and phenylalanine) that produce insulin when combined with carbohydrates. Other components of milk that might induce comedones include whey proteins and iodine.

Caffeine, theobromine, and serotonin found in chocolate may also increase insulin production.

Food containing fatty acids

Fatty acids are needed to form sebum. Studies show that some monounsaturated fatty acids, such as sapienic acid and some vegetable oils, can increase sebum production. However, the essential fatty acids linoleic, linolenic and gamma-linolenic acid can unblock the follicles and reduce sebum production.

What to eat if you have acne?

Some people with acne have reported improvement in their skin when they follow a low-glycaemic index diet and increase their consumption of whole grains, fresh fruits and vegetables, fish, olive oil, garlic while keeping their wine consumption moderate.

It’s a good idea to drink less milk and eat less of high glycaemic index foods such as sugar, biscuits, cakes, ice creams and bottled drinks. Reducing your intake of meat and amino acid supplements may also help.

How to treat different types of acne

Depending on the severity of the acne, there are a variety of over-the-counter and prescription treatments available to combat acne. 

Best ingredients for non-inflammatory acne, such as whiteheads and blackheads: 

  • Salicylic Acid: Penetrates pores to dissolve excess build up and clear out acne-causing bacteria. 
  • Benzoyl peroxide: This ingredient kills the bacteria that cause acne, helping remove excess oil and increases skin cell turnover. This ingredient can cause skin purging with possible side effects such as redness, burning and stinging, especially if you have sensitive skin. 
  • Tea tree oil: Especially useful for those days you feel a pimple brewing under the surface, tea tree oil reduces inflammation and prevents acne flare-ups. 
  • Sulfur: Sulfur removes dead skin cells that clog pores and helps remove excess oil. Products containing sulfur may cause dry skin and have an unpleasant odor.

Best ingredients for inflammatory acne, such as Papules, Pustules, and Cysts: 

  • Benzoyl peroxide: This ingredient calms down inflamed, angry breakouts and gets rid of the acne-causing bacteria.
  • Retinoids: Retinoids and/or Retinol work to increase skin cell turnover which helps reduce inflammation and reduce infection in the area. You can find retinol products over-the-counter, while the retinoids, which are stronger dosage, can only be prescribed by a dermatologist.

    For severe acne, a dermatologist may prescribe topical retinoid (tretinoin, which is prescribed for mild to moderate acne) and/or oral retinoid (isotretinoin, which is prescribed for severe or stubborn acne). In addition, a professional can perform acne extractions, chemical peels, and other procedures that can help with acne.