The exact cause of acne is mostly unknown. One exception is the occurrence of acne in women as a result of excess male hormone production, which is diagnosed by excessive growth of hair, especially in places not usual on a female, called hirsuitism; irregular menstrual cycles; and premenstrual flare-ups of acne.

A 2001 study demonstrated that menstrual cycle does affect acne. Surprisingly, the study revealed that 53% of women over age 33 experienced a higher premenstrual acne rate than women under age 20. Many alternative practitioners assert that acne is often related to a condition of toxicity in the intestines or liver.

This condition may be due to the presence of bacteria such as Clostridia spp. and Yersinia enterocolitica, a result of a low-fiber diet; a lack of friendly gut flora such as Lactobacillus spp.; an intestinal overgrowth of Candida albicans; and food allergies.

The interaction between the body’s hormones, skin protein, skin secretions, and bacteria determines the course of acne. Several other factors have also been shown to affect the condition:

• Age. Teenagers are more likely than any other age group to develop acne.
• Gender. Boys have more severe acne and develop it more often than girls.
• Disease. Hormonal disorders can complicate acne in girls.
• Heredity. Individuals with a family history of acne have greater susceptibility to the condition.
• Hormonal changes. Acne can flare up before menstruation, during pregnancy, and menopause.
• Diet. Although they are not the primary cause of acne, certain foods may bring on flare-ups or make the condition worse.
• Drugs. Acne can be a side effect of using antibiotics, oral contraceptives, and anabolic steroids.
• Personal hygiene. Use of abrasive soaps, hard scrubbing of the face, or handling pimples will often make them worse.
• Cosmetics. Oil-based makeup and hair sprays worsen acne.
• Environment. Exposure to oils and greases, polluted air, and sweating in hot weather can all aggravate acne.
• Stress. Emotional stress may contribute to acne.
• Friction. Continual pressure or rubbing on the skin by such objects as bicycle helmets, backpacks, or tight clothing can worsen acne.

The most common sites of acne are the face, chest, shoulders, and back, since these are the parts of the body where the most sebaceous follicles are found. In teenagers, acne is often found on the forehead, nose, and chin. As people age, the condition tends to appear towards the outer part of the face.

Adult women may have acne on their chins and around their mouths. The elderly often develop whiteheads and blackheads on the upper cheeks and skin around the eyes. Inflamed lesions may cause redness, pain, tenderness, itching, or swelling in affected areas.

There are no sure ways to prevent acne, but the following steps may be taken to minimize flare-ups:

• Gentle washing of affected areas once or twice every day.
• Avoidance of abrasive cleansers.
• Limited use of makeup and moisturizers; with avoidance of oil-based brands altogether.
• Frequent shampooing of oily hair which should be worn up, away from the face.
• A healthy, well-balanced diet that emphasizes fresh fruits and vegetables. Foods that seem to trigger flare-ups should be avoided.
• Gentle washing of the face, twice daily, with a soap compounded of sulfur, Calendula officinalis, or other substances that are useful against acne.
• Avoidance of handling affected areas excessively. Pimples should not be squeezed or prodded, as this may contribute to scarring, as well as spreading the acne lesions.
• Control over emotional stress.