Pimple, a small inflamed elevation of the skin. It may be solid (papule) or contain pus (pustule). Pimples occur primarily on the face, back, and chest. They are most common in adolescents, but also occur in children and adults. Many adolescents develop acne, a disorder characterized by the formation of numerous pimples and blackheads.

Pimples generally originate in hair follicles. They are caused by overactivity of the sebaceous gland, which secretes an oily fluid called sebum. They frequently result from a blackhead that has become inflamed or infected, often by bacteria on the skin surface.

The development of pimples is often associated with hormonal imbalances and various physical and emotional disturbances; in females, it is often linked with the menstrual cycle. Improper diet and poor hygiene also are often contributing factors. Squeezing pimples will worsen the condition, because it can damage delicate skin tissue as well as provide an opportunity for bacteria to spread.

Cold Sore, the common name for a small sore known medically as herpes simplex. Cold sores usually occur on or around the lips, although the cheeks, ears, or genitals may also be affected. A very painful condition known as a herpetic whitlow occurs when the palmar surface of a finger is involved.

Cold sores, sometimes called fever blisters, appear first as groups of tiny blisters, each group set on a small patch of red skin. These blisters are at first filled with a clear fluid and may later develop into pus-filled pimples. Within several days the blisters dry up and form yellowish or brownish crusts that drop off a week or two later.

Cold sores are caused by viruses that infect the nuclei of the cells of the epidermis. As indicated by their name, they are more likely to appear in a person afflicted with the common cold. However, they also occur in association with other febrile (fever-producing) diseases, such as influenza or pneumonia. In addition, they frequently follow a severe sunburn or occur with each menstrual period. It is believed that these conditions somehow lower the body’s resistance and allow the virus particles, which presumably have been dormant in the body, to become reactivated.