Acne vulgaris is the medical term for common acne, the skin condition that causes pimples, blackheads, and whiteheads when pores become clogged with oil and dead skin cells. It affects roughly 10% of adolescents and young adults worldwide, with the highest rates among 15- to 19-year-olds. The prevalence is about 25% higher in young women than in young men during this age range.
How Acne Forms in Your Skin
Every pore on your face, chest, and back connects to a tiny oil gland beneath the skin’s surface. These glands produce sebum, an oily substance that normally travels up through the pore to moisturize your skin. Acne develops when this process breaks down in a predictable sequence.
First, the cells lining the inside of the pore start shedding too quickly and clumping together instead of exiting smoothly. This creates a plug of dead skin and oil. Second, the oil gland keeps producing sebum that now has nowhere to go, so it builds up behind the blockage. Third, a bacterium called Cutibacterium acnes (C. acnes), which naturally lives on everyone’s skin, thrives in this oxygen-poor, oil-rich environment and multiplies. Fourth, your immune system detects the bacterial overgrowth and launches an inflammatory response, sending immune signals that cause redness, swelling, and pus.
C. acnes triggers inflammation through components in its cell wall that activate your immune system’s alarm pathways. This leads to the release of inflammatory signaling molecules that recruit more immune cells to the area, turning a simple clogged pore into a red, tender bump.
Types of Acne Lesions
Not all acne looks the same. The different types reflect how deep the blockage goes and how much inflammation is involved.
- Blackheads (open comedones): The pore is clogged but stays open at the surface. The plug of oil and dead skin oxidizes when exposed to air, turning gray, brown, or black. These are not caused by dirt.
- Whiteheads (closed comedones): The pore is sealed beneath the skin’s surface, trapping the oil and skin cells underneath. They appear as small, dome-shaped, skin-colored or whitish bumps.
- Papules: Small red, inflamed bumps without a visible center of pus. These form when the wall of a clogged pore breaks down and the surrounding skin becomes irritated.
- Pustules: Similar to papules but with a white or yellow pus-filled tip. This is what most people picture when they think of a “pimple.”
- Nodules and cysts: Large, painful lumps that form deep beneath the skin. Nodules are solid, while cysts contain fluid. These are the most likely to leave permanent scars.
What Causes It
Hormones are the primary driver. Androgens, a group of hormones that surge during puberty, directly stimulate the oil glands to grow larger and produce more sebum. This is why acne typically begins in the early teen years and peaks between ages 15 and 19. Hormonal fluctuations during menstrual cycles, pregnancy, and polycystic ovary syndrome can also trigger or worsen breakouts.
Genetics play a significant role. If both of your parents had acne, you’re more likely to develop it and to have more severe forms. Family history influences how your oil glands respond to hormones, how your skin sheds cells, and how aggressively your immune system reacts to clogged pores.
Other contributing factors include certain medications (particularly corticosteroids and some hormonal treatments), friction or pressure on the skin from helmets or tight clothing, and using heavy, pore-clogging skincare or cosmetic products.
Diet and Acne Severity
The connection between diet and acne has been debated for decades, but recent evidence points to a real, if modest, link with high-glycemic foods. These are foods that spike your blood sugar quickly: white bread, sugary drinks, white rice, and processed snacks.
In clinical trials, people who switched to a low-glycemic diet saw meaningfully better results. One 12-week study of 43 men with acne found that those on a low-glycemic diet had their total lesion count drop by 22 compared to about 11 in the control group. Another 10-week trial found a low-glycemic diet reduced acne severity by nearly 71% from baseline. Not every study has found statistically significant results, but the overall trend consistently favors lower-glycemic eating patterns. The effect is real but moderate, meaning diet changes alone are unlikely to clear severe acne.
How Severity Is Assessed
Dermatologists categorize acne severity to guide treatment decisions. While several grading systems exist, most break it down into familiar tiers. Mild acne involves mostly blackheads and whiteheads with only a few inflamed pimples. Moderate acne includes a noticeable number of inflamed papules and pustules spread across the face. Severe acne involves widespread inflammation, numerous pustules, and the presence of deep nodules or cysts.
One commonly used system counts inflammatory lesions on half the face: 0 to 5 is mild, 6 to 20 is moderate, 21 to 50 is severe, and more than 50 is very severe. Your dermatologist may also factor in scarring, how much of your face is affected, and the psychological impact when deciding on a treatment approach.
Treatment Options by Severity
Mild acne typically responds well to topical treatments applied directly to the skin. Products containing benzoyl peroxide kill acne-causing bacteria and help unclog pores. Retinoids (vitamin A derivatives) speed up skin cell turnover so dead cells are less likely to accumulate and form plugs. These can be used alone or in combination, and most people see improvement within 6 to 8 weeks.
Moderate acne often requires adding an oral antibiotic for a limited course to reduce the bacterial load and calm widespread inflammation. Hormonal therapies, including certain birth control pills, can be effective for women whose acne is driven by hormonal fluctuations.
Severe or treatment-resistant acne may warrant isotretinoin, an oral medication that dramatically reduces oil production, shrinks the oil glands themselves, and addresses all four underlying causes of acne simultaneously. It was approved for severe nodular acne that hasn’t responded to other treatments. Because it can cause birth defects, women of childbearing age must have two negative pregnancy tests before starting and monthly tests throughout treatment. All patients need blood work before and during treatment to monitor liver function and cholesterol levels. A typical course lasts 4 to 6 months, and for many people, the results are long-lasting or permanent.
Scarring and Prevention
Acne scars form when inflamed breakouts damage the deeper layers of skin. The body’s repair process can produce too little or too much collagen, leaving behind depressions or raised tissue. Scars are far more common with severe, deep acne and with picking or squeezing, which forces inflammatory material deeper into surrounding tissue.
Atrophic scars (indentations) are the most common type and come in three distinct forms. Ice pick scars are narrow, deep, V-shaped pits less than 2 mm wide that extend deep into the skin. Boxcar scars are wider, round or oval depressions with sharp vertical edges, typically 1.5 to 4 mm in diameter. Rolling scars are the broadest, usually wider than 4 to 5 mm, caused by bands of scar tissue pulling the skin surface downward and creating a wavy, uneven texture.
Each scar type responds differently to treatment. Ice pick scars, being so deep and narrow, are the most difficult to improve. Boxcar and rolling scars tend to respond better to resurfacing procedures. The most effective strategy for scarring is prevention: treating active acne early and aggressively before deep inflammation has the chance to cause permanent damage.
Who Gets It and for How Long
Globally, acne prevalence among young people has been rising steadily. The age-standardized rate increased from about 8,563 per 100,000 in 1990 to 9,791 per 100,000 in 2021. Western Europe has the highest rates, while regions with rapidly developing economies are seeing the sharpest increases, possibly linked to shifts toward more Western diets and lifestyles.
While acne is most common in teenagers, it doesn’t always stop at adulthood. A significant percentage of people continue to experience breakouts into their 20s, 30s, and beyond, particularly women. Adult acne tends to concentrate along the jawline and chin rather than the T-zone pattern typical of teenage acne. The good news is that acne, at any age, is treatable. Early treatment reduces the risk of scarring and the psychological burden that comes with persistent breakouts.