Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected with bacteria. Blockages and inflammation deep inside hair follicles produce cystlike lumps beneath the surface of your skin. Other pores in your skin, which are the openings of the sweat glands, aren't usually involved in acne.

Red bumps on the skin are common and could be a sign of irritation, inflammation, or an infection of the skin. There are a number of reasons why your skin may develop red bumps, including prurigo simplex, eczema, acne, viruses such as measles, and allergic reactions such as urticaria (hives).

An infected pimple happens when bacteria enter your skin, causing pain, redness and swelling. Popping, squeezing or picking at a pimple can lead to infection. You can treat mild infections at home with warm compresses and acne-fighting creams. Some infections require antibiotics.