Rosacea: This condition is characterized by pimples but not comedones and occurs in the middle third of the face, along with redness, flushing, and superficial blood vessels. It generally affects people in their 30s and 40s and older.
Pseudofolliculitis: This is sometimes called "razor bumps" or "razor rash." When cut too close to the skin, growing hairs twist into the skin and produce tender bumps. This is a mechanical problem, and treatment involves shaving less (growing a beard, laser hair removal). Pseudofolliculitis can, of course, occur in patients who have acne, too.
Folliculitis: Pimples can occur on other parts of the body, such as the abdomen, buttocks, or legs. These represent not acne but inflamed follicles. If these don't go away on their own, doctors can prescribe oral or external antibiotics, generally not the same ones used for acne.
Gram-negative folliculitis: Some patients who have been treated with oral antibiotics for long periods of time develop pustules filled with bacteria that are resistant to the antibiotics that were previously used. Bacterial culture tests can identify these germs, leading the doctor to prescribe different antibiotics or other forms of treatment.