Acne occurs when oil, dead skin cells, and bacteria become trapped inside hair follicles, resulting in infection and inflammation.

Although acne often develops on the face, it can affect hair follicles on other parts of the body, such as the chest, back, and shoulders.

Below, we describe what acne is and the types of acne that may develop on the shoulders. We also explore the symptoms and appearance of shoulder acne and list some treatment options.

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Pores are small openings in the skin. Each pore contains a single hair that sits inside a hair follicle. These hair follicles connect to oil-producing glands, called sebaceous glands.

Sebaceous glands secrete an oil called sebum, which carries dead skin cells to the surface of the skin.

Sometimes, sebum and skin cells form a plug within the hair follicle. This plug traps dirt and bacteria inside the skin, resulting in an infection. The infection triggers inflammation — in the form of a pimple.

Two types of acne can develop on the shoulders: acne vulgaris and acne mechanica.

Acne vulgaris

Acne vulgaris is the medical term for common acne. It typically occurs when oil and dead skin cells become trapped inside a pore or hair follicle.

Also, Cutibacterium acnes bacteria can trigger or worsen the symptoms.

In addition, changes in the levels of certain hormones can trigger breakouts. Some hormones that may influence acne vulgaris are:

Testosterone

Testosterone regulates sebum production, and rising testosterone levels can trigger acne breakouts in anyone.

Adolescent males may, for example, experience acne during puberty, when testosterone levels naturally increase.

Females with polycystic ovary syndrome may also develop acne due to high testosterone levels.

Progesterone and estrogen

The hormone progesterone can also contribute to acne.

Progesterone levels peak during the luteal phase of the menstrual cycle, which begins after ovulation and ends just before a period. As a result, acne breakouts may occur around this time.

In addition, some people experience acne while using progesterone-only hormonal birth control, sometimes called the mini-pill.

Meanwhile, the hormone estrogen has a converse effect — it inhibits sebum production and shrinks the sebaceous glands.

Other hormones

Other hormones that can play a role in acne include:

  • Insulin and insulin growth factor 1: These promote the growth of the sebaceous glands.
  • Melanocortins: These hormones regulate oil production in sebaceous gland cells.
  • Corticotropin-releasing hormone: This stimulates testosterone production and subsequent sebum production.

Acne mechanica

Acne mechanica develops in response to physical factors, such as:

  • pressure
  • friction
  • heat

These can damage the skin and trigger excess sebum production.

Some specific causes of acne mechanica include:

  • pressure or friction from a heavy backpack or purse
  • irritation from pillows or blankets made from rough or irritating fibers
  • excess heat and pressure from tight or restrictive clothing
  • excess heat and moisture from sweating, especially if a person does not immediately shower or change their clothes after physical activity

Not all acne looks or feels the same. Acne pimples vary in size, color, and severity.

Different types include:

  • Blackheads: These are small, round bumps with black spots in the centers. Each spot is oxidized sebum, not dirt.
  • Whiteheads: These are small, round bumps with white centers. They are firmer than blackheads and will not empty if a person squeezes them.
  • Papules: These are small red bumps that may feel sore or tender.
  • Pustules: These are small bumps with an inflamed base and a white, pus-filled head.
  • Nodules: These are large, hard lumps deep within the skin. Nodules can be tender or painful to the touch.
  • Cysts: These are large, pus-filled lumps that may cause scarring.

Below are some treatment options for shoulder acne.

Topical treatments

Over-the-counter topical treatments — usually creams, gels, or foams — can help clear acne breakouts. Look for products that contain:

Benzoyl peroxide

Benzoyl peroxide is an antiseptic that kills C. acnes bacteria on the surface of the skin and inside hair follicles.

In 2017, a 12-week clinical trial investigated the effectiveness of this antiseptic as a treatment for acne vulgaris among 607 participants.

The researchers found that using a benzoyl peroxide cream resulted in a 72.7–75.0% reduction in inflammatory lesions, while the use of a placebo cream resulted in a 41.6% reduction in inflammatory lesions.

Salicylic acid

Salicylic acid is a beta-hydroxy acid that reduces sebum production and skin inflammation.

It also reduces acne lesions by exfoliating the skin — removing oil, dirt, dead skin cells, and bacteria.

A 2018 clinical trial compared the effectiveness of a salicylic acid cream and a benzoyl peroxide cream for the treatment of mild to moderate acne. The trial included 31 participants, and all applied each cream to separate sides of their faces for 28 days.

The researchers found that the 2% salicylic acid cream reduced the number of papules and pustules by 47.9% and reduced the number of noninflammatory lesions by 43.1%. These results were comparable to those of the benzoyl peroxide cream.

The team concluded that the two creams were similarly effective in treating acne.

Retinoids

Retinoids are a class of chemical compound derived from vitamin A. They increase skin cell turnover, keeping dead cells, oil, and bacteria out of pores.

A person needs to use a retinoid consistently to see results. This is not a spot treatment.

Azelaic acid

Azelaic acid exists naturally in grains, such as wheat, barley, and rye. Topical application helps decrease redness and swelling of the skin.

A small 2017 pilot study investigated the safety and efficacy of a 15% azelaic acid foam in the treatment of mild acne on the torso.

The results showed that 44% of participants who applied the foam twice daily experienced a significant reduction in their acne.

Oral medications

The following prescribed medications, which come in pill form, can help treat the underlying causes of acne.

Care strategies

The American Academy of Dermatology provide the following tips for managing acne:

  • washing the skin twice a day and as soon as possible after sweating
  • rinsing the skin with lukewarm water
  • avoiding harsh skin care products, such as astringents, toners, and exfoliants
  • regularly shampooing the hair
  • limiting or avoiding tanning
  • avoiding picking or popping pimples

To help prevent shoulder acne, try:

  • wearing lightweight, breathable clothing
  • immediately changing out of sweaty clothes
  • applying sunscreen to the shoulders during hot weather
  • keeping the hair clean to avoid getting excess oil on the shoulders
  • avoiding using bags with shoulder straps, especially when carrying heavy items
  • avoiding scrubbing or scratching the skin, which can irritate the area and introduce dirt and bacteria into existing pimples

Shoulder acne may clear up on its own or with the help of over-the-counter products.

However, contact a doctor if acne persists or worsens despite home treatment or more than one painful acne lesion develops.

A doctor may prescribe a stronger treatment for more severe acne. Or, they may refer the person to a dermatologist — a doctor who specializes in treating skin conditions.

Acne occurs when oil and dead skin cells form a plug inside a pore or hair follicle. This plug traps dirt and oil beneath the skin. A bacterial infection can develop in the affected pore, which can lead to inflammation and swelling in the form of a pimple.

Two types of acne can develop on the shoulders: acne vulgaris and acne mechanica. The first typically develops in response to hormonal changes, while the second usually develops in response to heat, pressure, friction, or a combination.

Shoulder acne does not look or feel the same for everyone. Some people develop small pimples, while others with more severe acne develop pustules, nodules, or cysts. More serious acne can be extremely painful and require stronger treatments.