When the skin produces too much sebum and does not shed dead skin cells quickly enough, it can build up in the hair follicles, causing a plug to form. This plug can cause the hair follicle to swell and form a white pore or, if the plug is open on the surface, a dark or black pore. A common misconception is that black pore is caused by the skin being dirty and that the black is dirt. This is not the case, but rather it is simply the skin's pigment (melanin) that oxidizes and turns dark when open pores come into contact with oxygen in the air.

The reason why the area around the blackhead becomes inflamed is often because bacteria and fungi like the oily environment around the blackhead and grow. This can lead to pus formation and also inflammation of the skin around the pimple (papules/pustules).

A blockage or inflammation that develops deep within the sebaceous glands can form lumps under the skin's surface called cysts.

Hormonal influence

Testosterone or other androgenic hormones stimulate the sebaceous glands to produce more sebum than is necessary. During puberty, hormonal changes occur in both boys and girls, and the sebaceous gland, which is sensitive to these hormonal changes, then produces more sebum.

Oily skin is therefore a very common skin condition during puberty or the years thereafter, which increases the tendency to get blackheads and acne.

Hereditary influence

There is some evidence that heredity plays a major role in the development of blackheads and acne. If both parents suffered from acne during puberty, it is likely that their children will also develop acne.

Although the main causes of acne-prone skin tend to be hormonal or hereditary, there are a few other factors that have been shown to worsen symptoms; this applies primarily to diet and various skin care products. When it comes to diet, it is very individual, but there are studies that show that certain foods in combination with oily skin increase the risk of acne.

However, we always recommend that you not only change your diet but combine it with medical treatment if you suffer from acne that requires medical treatment. This is to minimize the risk of scarring.

It is always a good idea to consult a dermatologist, even for mild and early symptoms (to prevent the condition from getting worse), but there are some rules that are good to follow:

• Leave the pimples alone – don't touch or squeeze them, this increases the risk of worsening inflammation and an even worse condition

• If you experience cysts under the skin or if the pimples do not heal normally or form scars, it is important that you get medical help. Diagnosed acne may require medical treatment in the form of isotretinoin or other drug treatment. Unfortunately, scars are difficult to do anything about once they have appeared, which is why it is important to start medical treatment in time.

Scars are unfortunately difficult to do anything about once they have appeared, which is why it is important to initiate medical treatment in a timely manner.

• Use non-comedogenic makeup, i.e. makeup that does not clog pores.

• Use sunscreen designed for oily and acne-prone skin. It is best to avoid using sunscreen on your skin during the winter months (in Sweden) – exceptions are in the mountains (high altitude) or when the sun is reflected off the snow.

Contrary to popular belief, toothpaste does not help dry out rashes. There is no medical evidence to suggest that it does. In fact, toothpaste contains substances that can irritate and damage the skin.

More information in the Skin Bible

The Skin Bible contains more tips regarding diet and acne-prone skin.