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 close to the skin, curly neck hairs bend under the skin and produce pimples. 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 develop pustules filled with bacteria resistant to the antibiotics which have previously been used. Bacterial culture tests can identify these germs, leading the doctor to prescribe different antibiotics or other forms of treatment.
source : medicinenet
