Dark pimples on the buttocks are common and are usually not a cause for concern. Most cases are easy to treat at home. If they get infected and progress to a boil, however, they might have to be treated by a doctor.
The Skin Process
The most common pimple on the buttocks is similar to acne. Like acne, teens get pimples on their bums more often than adults.
Dark Pimple Formation
Many dark pimples on the buttocks begin as inflammation or infection in a hair follicle (folliculitis) and can progress to nearby skin cells. Build-up of inflammatory cells and oil (sebum) from the sebaceous gland causes a pimple to form. The process can involve a single follicle or several at once.
Some dark pimples on the buttocks start in the skin outside of the hair follicle. Pimples that start outside of a hair follicle are usually caused by infection from bacteria, a fungus or irritants that penetrate the skin surface.
Folliculitis most often involves just the superficial layers of the hair follicle. Infection in a blocked follicle can progress to deeper layers, or affect surrounding skin layers (peri-folliculitis). Similarly, infection that starts in skin outside a hair follicle can travel to surrounding tissues.
Wherever the infection is located in the skin it can have pus at the point (pustule). This can drain without treatment. If the inflammation or infection goes further and deeper, the pimple can form a tender, or painful boil (abscess).
After the initial process resolves, a persistent, hard, darkened pimple might remain under the skin. It can disappear over time.
Pimples begin as small, red bumps under the skin. The inflammatory or infectious process causes more melanin production, especially in darker skins. The increased melanin leads to darkening (post-inflammatory hyperpigmentation) of the pimple and sometimes the surrounding skin. The area can also get darker or scar if you pick or squeeze the pimple.
Folliculitis results from a blocked pore that then becomes infected. Other pimples that start outside the follicle can be caused by infectious organisms, or by skin trauma, skin allergens and other irritants.
Bacteria and fungi feed on dead skin cells and debris and infect a clogged pore. They can also infect the follicle through an abrasion after you scratch the itchy, inflamed pimple. Organisms similarly infect irritated or traumatized skin outside a follicle.
The more common infecting organisms include:
- Staphylococcus aureus, the most common skin bacteria, is a frequent cause of folliculitis. These bacteria live in your nose, so you can infect your skin if you pick your nose and scratch your bum.
- Pseudomonas aeruginosa is a less common infecting bacteria. It is usually picked up in contaminated, under-chlorinated swimming pools, hot tubs and spas. With this type of infection, there are usually multiple red pimples over the buttocks, back and other areas that darken as they heal.
- Pityrosporum ovale, a common skin yeast, can infect hair follicles and cause folliculitis, though they occur more commonly on the upper chest and back than on the buttocks.
- Candida, another skin yeast, can cause a skin rash or a pimple if it infects the follicle.
These infectious organisms can pass from one person to another.
Like acne on your face, dirt, dead skin cells, or products with coal tar or petrolatum jelly, can clog your hair follicle. Oil (sebum) from the sebaceous glands can't get out. The follicle becomes inflamed and a pimple forms and sometimes gets infected.
Other Potential Causes
In addition to infection, other potential causes of dark pimples on buttocks include:
- Skin trauma from sitting a long time
- Rubbing or scratching your bum
- Sleeping naked on dirty bed linen that may contain bacteria and fungi
- Long-term use of steroids (creams, oral or injections)
- Moisture and bacteria trapped under surgical tape used to cover a wound
- Allergic reactions to products, environmental factors, or drug exposure
In many cases dark pimples on your buttocks will heal without treatment. If they don't, you can easily treat them with home remedies and over-the-counter (OTC) medicines. Sometimes you need a combination of treatments or to be treated by a doctor.
- Warm compresses decrease inflammation and soften the pimple to help it drain. Wet a soft wash cloth in warm water and gently press it on your pimple(s). Re-warm the cloth when it cools and repeat the process for about 15 minutes.
- Soak in a bath tub of moderately warm water for 15-20 minutes (sitz bath). Adding a small amount of Epsom salts or vinegar can be helpful.
- Wash gently with an antibacterial soap or antiseptic solution to decrease the skin bacteria.
You can use any of these OTCs in addition to home remedies. Use until pimples heal which should take only a few days. Apply products to clean, dry skin. Massage in gently and thoroughly.
- Apply benzoyl peroxide or salicylic acid cream.
- Use a topical antibiotic like Neosporin or Bacitracin if there are signs of infection. These products can help a mild infection and help prevent scarring. Apply two to four times daily.
- Use Miconazole or another an antifungal cream such if an accompanying skin rash suggests a yeast infection. This type of treatment can clear a fungal outbreak. Apply two times daily.
- After your pimples start to heal, Hydrocortisone cream or lotion 1% or 2% can decrease the inflammation and lighten the hyperpigmentation. Apply very sparingly twice a day. Don't use if your pimples are caused by steroids.
- A 2% hydroquinone cream such as Ambi can also lighten hyperpigmented areas over time. Apply sparingly twice a day after pimples are healed.
Common pimples that resolve easily are of minor concern. A history of similar breakouts, exposure, trauma, infections on other parts of your body, or a chronic illness can frequently pinpoint an underlying cause.
For harder-to-diagnose or treat situations you may need an exam by a doctor. If there is infection, a culture of the pus can sometimes identify the bacteria. He can also examine hair follicles under a microscope to identify a fungus.
When to See a Doctor
See a doctor for evaluation and treatment if:
- Home remedies or OTCs don't work
- Pimples get large and painful or drain pus, suggesting a boil or abscess
- Pimples form a large, hard painful knot that won't go away
- Pimples frequently recur, making it hard to sit and interfering with your daily life
- Pimples get worse and/or you have a medical condition that puts you at risk
Your doctor may suggest cutting a boil open (lancing) to allow the pus to drain. He may also prescribe antibiotics by mouth for an infection. If a fungus is seen he can prescribe a stronger antifungal cream or oral medicine.
People who are prone to acne on their face are usually prone to skin eruptions on other parts of the body. Some medical conditions also lead to an increased risk for dark pimples:
- Obesity: People who are obese tend to sweat, trapping moisture and infection in their clothes.
- Diabetes: People with diabetes have an increased risk of skin infections.
- Hormonal disorders: Women with disorders that cause increased male hormones, such as polycystic ovarian syndrome (PCOS), tend to have oily skin. They are more prone to folliculitis.
- Immune disorders: People with HIV/AIDs, cancer, leukemia and other blood disorders are more prone to folliculitis, as are those who take and anti-cancer drugs.
Other factors that lead to an increased risk of dark pimples forming on the buttocks include:
- Dirt remaining on your skin for a long time
- Trauma from scrubbing your skin too roughly
- Trapped heat and moisture from prolonged, tight clothing
- Friction and skin inflammation from wearing tight jeans, coarse underwear or no underwear
- Friction from riding a bike or from exercise that leads to skin abrasions and infection
- Scratching or rubbing your skin
- Shower daily to keep your skin free from dirt, dead skin and other irritants.
- Wash your skin gently to avoid abrasions or cuts.
- Change your bed linens frequently.
- Keep your skin dry.
- Avoid products that caused a breakout.
- Try to avoid oils, ointments and preparations with coal tar or petroleum jelly, as these substances can clog your pores.
- If you ride a bike or sit for a long time, wear soft, comfortable, breathable clothing to prevent skin irritation and abrasions.
- Wear cotton underwear so that warm moisture that encourages bacteria to grow is not trapped on your skin.
- Avoid sharing wash cloths, towels and other personal items to prevent the spread of bacteria and fungi.
- If you get recurrent infections check the chlorination in your pool and avoid community pools, hot tubs and spas or shower well after using them.
- To prevent bacterial infection or further darkening of the skin, avoid picking or squeezing pimples or scrubbing your skin hard.
You can easily take care of dark pimples on your buttocks at home. If they are recurrent, take preventive steps to avoid permanent hyperpigmentation and scarring. If you are concerned because pimples frequently recur, won't go away, or get worse, see your doctor for treatment and to rule out more serious conditions.