Acne is a disorder of the hair follicles in which comedones (blackheads) develop in the skin. When there is increased flow from the sebaceous (oil) glands in the dermis combined with increased shedding of dead skin cells, the oil-cell mixture can block the opening of the follicle and form a comedo (plural, comedones). If the clogged follicle becomes infected with bacteria, inflammation and a closed pus-filled comedo (pustule) may develop.

Causes and Risk Factors

Teenagers develop acne at a higher rate than other age groups. This is because hormone production during puberty increases the output of the sebaceous glands and the rate of skin-cell turnover within the follicles. However, children as young as 5 years old and adults can develop acne as well. In young women, it often worsens and improves with the rise and fall of hormone levels during the menstrual cycle.

There is a genetic predisposition for acne; that is, people whose family members have acne are also likely to have it.

Stress may also significantly affect acne. The condition often worsens during times of stress and improves during more stable periods.

Many people believe that poor dietary habits can cause acne. Foods with high sugar and fat content, such as chocolate, are thought to affect the skin follicles. However, there is no clinical evidence to support this. Studies show no connection between junk food and acne. Some patients find that certain foods, such as dairy products, worsen acne.

Propionibacteria acnes is the common bacterial cause of skin infection that accompanies acne. These bacteria are present whether the patient has adolescent, persistent, or adult-onset acne.

Signs and Symptoms

The first sign of acne is comedones. They appear most often on the face, chest, back, and shoulders. Bacteria populations can grow quickly in comedones. If the follicle wall ruptures, an inflammatory lesion develops. Redness, swelling, and pus-filled lesions accompany infection.

Inflammation that persists can result in the formation of a large, often painful acne cyst or nodule (a collection of inflammatory cells). When a cyst heals, it can leave a pitted, discolored scar, known as a pockmark. Scars can be treated with dermabrasion, laser resurfacing, or collagen injection.

Diagnosis