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What causes acne? What are the types of acne?

p acnes causes acne

Like many other diseases, acne is caused by a complex interaction of multiple factors. The leading causes of acne are genetics and hormones. These two factors increase the size of the oil glands on the skin. Accumulation of dead skin cells in the skin's oil glands' opening, combined with excess sebum production, clogs the skin pores. A special kind of bacteria, Propionibacterium acnes (P. acnes), which lives in our skin oil glands, proliferates in these enlarged clogged oil glands, triggering our immune response system, leading to skin irritation and the typical red acne pimples.

Increase in sebum production:

One of the most important factors in the development of acne is the production of sebum, a type of oil that is produced by the sebaceous glands in the skin. People with acne tend to produce higher amounts of sebum than those without acne, and the composition of the sebum is different as well. It contains high amounts of squalene and low amounts of linoleic acid. When free radicals react with sebum, it causes inflammation in a process known as lipid peroxidation. This inflammation leads to the formation of pimples and other types of acne lesions.

Clogging of the skin's oil glands:

In addition to sebum production, another factor that contributes to acne is the stickiness of skin cells inside the pores. Skin cells inside the pores can stick together, a condition known as follicular hyperkeratosis. This creates a bottleneck that traps oil in the follicle, leading to the buildup of oil and the growth of acne-causing bacteria. Low levels of linoleic acid in the sebum and low ceramide levels in the skin have been implicated in this process.

More bacteria:

Acne-causing bacteria, specifically P. acnes (or C. acnes), are also involved in the development of acne. While these bacteria live within the follicles on everyone's skin, people with acne may have different strains on the skin and react to them more, leading to inflammation. Although C. acnes is involved in the development of acne, acne is not an infection, and it cannot be caught or spread.


Inflammation is another factor that plays a role in acne development. Sebaceous glands are more than just oil factories - they react to hormones and acne-causing bacteria, leading to inflammation that causes pimples. This inflammation can occur even in normal-appearing skin in people with acne. Under the microscope, inflammation can be seen around the oil glands even before any visible pimples form.

Hormones and acne:

Hormones play a major role in the development of acne. Androgen hormones, such as testosterone and dihydrotestosterone, bind to receptors on the oil glands, leading to increased oil production and inflammation. These hormones are present in both men and women, but women often experience acne flares around the time of their menstrual periods because of increases in hormone levels that trigger oil gland activity. Dermatologists may prescribe hormonal therapies by mouth to treat acne by regulating the levels and activity of these hormones.

Diet and acne:

Diet is another factor that can contribute to acne development. Foods with a high glycemic index, such as those high in refined sugars and starch, raise blood sugar and promote inflammation in the skin. High sugar concentrations in the blood increase levels of insulin-like growth factor-1 (IG-1), which is known to activate oil glands through a messenger called SREBP. This means more oil production and inflammation in the skin, worsening acne. Cow's milk, particularly skim milk, has also been associated with acne.

Interestingly, yogurt and cheese are not associated. Whey protein and Vitamin B12 supplements may also contribute to acne breakouts. In contrast, studies of hunter-gatherer societies that eat fresh fruits, vegetables, and whole grains have shown that acne is almost non-existent in these societies, suggesting that the Western diet is a major contributing factor for the development of acne.

Stress and acne:

Stress is another factor that can contribute to acne development. Cortisol, a hormone that is produced in response to stress, activates the oil glands and leads to more oil production as well as inflammation that causes acne. Stress-related acne is well-documented, and managing stress through relaxation techniques, exercise, and other stress-reducing activities may help improve acne.

Environmental factors:

Environmental factors such as pollution, humidity, and exposure to ultraviolet radiation can also contribute to acne development. Air pollution can clog pores and trigger inflammation, while humidity can increase oil production. Ultraviolet radiation can cause skin damage and inflammation, which can worsen acne. Protecting the skin from environmental factors may help reduce the risk of developing acne.

What are the different types of acne lesions?

The most common acne lesions are whiteheads, blackheads, papules, pustules, nodules, and cysts.

  • Whiteheads: Whiteheads are clogged oil glands covered by a thin layer of skin that appear as white bumps or spots.
  • Blackheads: Blackheads, aka open comedones, are usually located on the face but can appear on the neck, chest, and back. Blackheads are skin pores clogged by dead skin cells and dry sebum. The oxidation of sebum exposed to the air - gives the blackheads a typical color.
  • Papules: Papules are small and inflamed lesions. They are usually sensitive and painful.
  • Pustules: Pustules are red pimples that contain pus. Pustules are usually larger than papules and have the typical pus-filled yellow dot on their top.
  • Nodules: Nodules are cyst-like lesions situated under the skin. They don't contain pus, are hard to the touch, and are painful.
  • Cysts: Cysts are inflamed, broader, and deeper painful acne lesions. These lesions are usually part of severe and cystic acne and can leave long-term acne scars.

different type of acne lesions infographic

What are the most common types of Acne?

Acne vulgaris is classified by grades of severity and divided into three primary classes: mild, moderate, and severe. Acne with only white and blackheads is called noninflammatory acne, and acne that includes papules, pustules, or cysts is called inflammatory acne.

  • Mild acne: People with mild acne usually have less than 20 comedones and 15 lesions. Moderate acne: People with moderate acne typically have 20 - 100 comedones and 15 - 50 papules or pustules.
  • Severe acne: People with severe acne usually have > 50 papules or cysts combined with 2-5 cysts.
  • Cystic acne: Cystic acne is a type of severe acne with more than five deep inflamed cysts.
  • Acne fulminans: Acne fulminans is another rare variant of severe acne. It happens when many acne pimples develop at a very rapid pace on the chest and back. It occurs more in your males and can be accompanied by painful joints, fever, and scarring.
  • Acne mechanica: Acne mechanica is a type of acne that causes acne and is triggered by pressure and friction on the skin. It is frequently aggravated by heat and humidity. Acne mechanica is characterized by small bumps ranging from tiny comedones to inflamed lesions. It is common in athletes who wear football or baseball hats and now in people who wear coronavirus face masks. Covid induced acne, also called maskne, can be reduced using special copper and silver-infused anti-acne masks.
  • Acne Conglobata: Acne Conglobata is the most severe form of acne. It is a very severe and deep cystic acne. It is characterized by many deep and inflamed cysts, all connected underneath the skin's surface.

How does Acne start?

The first step in acne is the androgen-induced enlargement of the sebaceous glands with the overproduction of sebum. In the second phase of acne, the sebaceous glands' opening is clogged by dry oil, dead skin cells, and dirt, forming the infamous comedones.

The comedones (Commonly called whiteheads and blackheads) are plugs made of keratin, sebum, and bacteria. Comedones exposed to the skin surface and have a central black appearance (Due to the oxidation of tyrosine to melanin by tyrosinase) are called "blackheads" or open comedones. However, comedones that remain underneath the skin surface are called "whiteheads" or closed comedones.

What is the role of bacteria in acne?

The third acne phase includes the proliferation of acne bacteria—Propionibacterium acnes (P. acnes). Most P. acnes reside in the hair follicle's opening, an area rich in lipid nutrient sources and poor in oxygen (An ideal site for anaerobes). P. acnes is involved in developing inflammatory acne by activating complements and metabolizing sebaceous triglycerides into fatty acids that irritate the follicular wall and surrounding dermis. P. acnes produces lipases, proteases, and hydrolases, contributing to inflammation and tissue destruction and expressing stress proteins responsible for comedonal rupture and inflammatory response.

What causes red, painful pimples?

In the fourth phase of acne, pilosebaceous follicles are surrounded by macrophages and inflammatory mediators expressing Toll-like receptors (TLR2) on their surface. TLR2 activation leads to transcription of nuclear factor triggering and thus heading toward the expression of cytokines (Such as interleukin-1β (IL-1β), IL-8, and granulocyte macrophage-colony stimulating factor (GM-CSF)) initiates and propagates the inflammatory response. The inflammation in and around the sebaceous gland further stimulates keratinocyte hyperproliferation. The enlargement of the sebaceous gland, the ruptures of its walls, and the following inflammatory response cause different acne lesions, papules, pustules, and nodules.

Which treatment is the best for your acne type?

The best treatment for your acne will be an acne treatment personalized to your type of acne, acne severity, skin type, gender, and age. One size fits all products that people buy online or at drugstores are frequently irritating or simply ineffective in the drugstore. Apps like MDacne, analyze your skin and provide personalized acne treatment directly to your doorstep. Using the app algorithms and a medical support team, subscribers received continuous free fine-tuning of the medications, allowing faster and better results than the counter treatment option.

What are the best ingredients for the treatment of acne?

The essential acne treatment combines a medicated acne cleanser, a non-comedogenic active daily moisturizer, and a medical-grade anti-acne treatment cream. More than 80% of acne people can expect improvement with over-counter medication, while 20% would need to see a dermatologist and get prescription medication.

According to the American Academy of Dermatology, benzoyl peroxide is the most effective single anti-acne topical medication. The most common topical medications dermatologists use for acne treatment are benzoyl peroxide, salicylic acid, niacinamide, and retinoids.

The most common oral medications dermatologists use are the tetracyclines: minocycline and doxycycline, erythromycin, and isotretinoin (Accutane). Women with adult acne can also be treated with spironolactone, oral contraceptives, and DIM supplements.

Which treatment is the best for acne scars and dark spots?

People with acne's first goal is to heal current active poles and prevent new pimples from forming. Once the active acne is under control, post-acne signs frequently need to be addressed. Fortunately, there are good options to face post-acne dark pots. Those usually include a dark spot remover with hydroquinone or arbutin combined with a retinoid and an oil-free sunscreen. Treatment of real acne scars is usually more complicated and requires in-office dermatologist treatment with minor needle radio recent devices or lasers.

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