Acne assails the skins of millions of people across the world. And all of them begin with a comedo, which develops as a result of clogged pore. A comedo actually remains there under the skin for quite some time without creating any problem. When the conditions are right and bacterial infection takes place, it develops into an inflamed lesion. Oil is continuously produced by the skin, which makes the bacteria to flourish better and the problem aggravates further. At the same time the skin around the affected part wages a war against the infection which makes it even more painful for the sufferer.

There are two broad categories of acne: Inflammatory Acne and Non-Inflammatory Acne. Among the inflammatory kind, the mildest ones are papules. These are pink, small bumps on the skin and can be rather tender to touch. Much like papules are the pustules. The only difference being that they are inflamed and pus-filled. The inflammation in pustules is not caused by bacteria but by irritation due to the presence of sebum and its component, like fatty acids.

Cysts are another kind of inflammatory acne. But they are far more painful kind, as they are large, filled with pus and lodged deep in the skin. Nodules are like cysts but are the most severe form of acne. They spread in a larger area and are deeply inflamed. They may take weeks and even months to disappear. Cysts and nodules may leave scars behind.

Non-inflammatory acne may occur in the form of whiteheads or blackheads. Whiteheads are plugged follicles under the skin surface while blackheads appear on the skin surface. The black appearance of blackheads is not due to the presence of bacteria but due to the presence of melanin. The non-inflammatory kind of acne is not painful though they look very ugly and that's the worst part about them.