Let´s take a look at 7 of them:
1. Acne normally begins between the ages of eleven and thirteen.
This is true in both males and females due to changes in hormone levels. These hormones, called androgens, will enlarge the facial glands. The oil produced by the glands is known as sebum. The hair follicles shed dead cells too quickly and the cells and sebum form a blockage in the gland.

2. Pressure and rubbing from tight garments.
Adult with acne should avoid tight-collared shirts that might irritate the acne further. Adult athletes may notice an outbreak of acne from equipment such as backpacks or athletic helmets.

3. Acne can also be caused by genetics.
Studies have shown that a family history of acne can affect whether you have acne and the severity of it. So if your mother or father had acne as a teen, chances are that it will be a contributory factor to the cause of your acne.

4. Factors linked to women
Women have several factors that men don’t that can be linked to the cause of acne. Women go through several phases of life that cause their hormone levels to change. These changes can cause acne in adult women between two and seven days before their menstrual cycle.

5. Pregnancy and hormones

Pregnant women also experience a fluctuation in hormones. Those who may have previously had little or no acne may see pimples during their pregnancy and for a time after the birth of the baby until the hormone levels return to normal.

6. Menopause and hormones
Menopause will cause changes in hormone levels for woman and can be a cause of acne. Women also tend to wear heavy makeup when experience an acne outbreak, which only worsens the problem by further clogging pores.

7.Stress.
Especially in adults, stress can be another cause of acne. When you are stressed, the hormone cortisol is produced. Cortisol will worsen any acne you already have. To prevent stress-related acne, try relaxation and meditation. Some adults experience acne from picking at blemishes on their skin. You should never pick at or squeeze a pimple, blackhead or any other blemish on your face.

This can only cause more acne and possibly an infection. When cleaning your face, avoid harsh facial cleansers (they cause the creation of more sebum) and scrubbing your face too vigorously.

Acne treatment:
The sad part is that most of the acne products are sold over the counter for treatment. Most over-the-counter acne treatments are topical and come in the form of a cream, soap, lotion or gel. Acne products normally contain benzoyl peroxide (good for killing the bacteria and possibly reducing oil production), sulfur (helps eliminate blackheads and whiteheads) and/or salicylic acid (cuts down the speed of cell lose). More severe cases may require prescription acne medicine that is topical or oral. Oral acne medication can help reduce both the growth of the bacteria and inflammation of glands.