Acne starts with a basic infection: blackheads or pimples. They appear due to the enlargement of pores that are covered by grease, dead skin cells or bacteria. Invisible to the naked eye, the pimple prowls under the skin surface, waiting for the right moment to grow and become an infection. While the skin keeps producing grease, bacteria blossoms inside the inflamed pore. The skin surrounding the area expands the inflammation until white blood cells start fighting the intruding bacteria.
Even though pimples are essentially born the same way, they may take different forms and react differently according to the person who has them.

Without inflammation
- Closed or whiteheads: If a closed follicle is kept below the skin surface, this inflammation is called “closed acne” or a “whitehead.” Usually, they surface to the skin as small white lumps.

- Open or blackheads: If the closed pimple is enlarged and pushes itself to the outside surface of the skin, it’s called a close acne or a blackhead. The problem with blackheads appearance is nor exactly related to that of a dirty skin, but of excessive melanin, thus the dark pigment of the skin.

With inflammation
- Furuncle: The most common type of acne with inflammation is a furuncle, which surfaces the skin as a small pinkish inflammation. They may feel sensitive to the touch and are usually considered a step between infections without inflammation and the clear irritated ones.

- With pus: As furuncles, these are small infections. However, differently from furuncles, they are clearly irritated and contain pus. They may have a colored base, with a yellowish or whitish center. Pimples with pus usually contain a great quantity of bacteria. In most cases, inflammation is caused by the chemical irritation of sebaceous components, such as fat-free acids.

- Lumps or nodules: Big and often sore, lumps are always irritated, filled with pus and deep infections. Lumps are discovered when the contents of a pimple outpour to the surrounding skin and the local immune system starts reacting to it by producing pus. This is the most severe case of acne and lumps may persist for weeks or months, maybe aggravating into a deep nodule. Both lumps and nodules usually leave deep scars.