If you really must do something about your pimple beyond washing your face and spot treating, ice or a cold compress can help reduce swelling. Wrap an ice cube or the compress in a soft tissue or cloth and apply it to your zit for 20-30 seconds at a time, a few times a day. In case of an emergency (like, prom), you can also see a dermatologist for a cortisone injection, which can help shrink the cyst down quickly in a day or two.
Rosacea, although distinct from acne, does have some similarities. Unlike common acne, rosacea occurs most often in adults (30-50 years of age). Unlike acne vulgaris, rosacea is devoid of blackheads and characteristically does not resolve after puberty. Rosacea strikes both sexes and potentially all ages. It tends to be more frequent in women but more severe in men. It is very uncommon in children, and it is less frequent in people with dark skin.
Acne (acne vulgaris, common acne) is a disease of the hair follicles of the face, chest, and back that affects almost all teenagers during puberty -- the only exception being members of a few primitive Neolithic tribes living in isolation. It is not caused by bacteria, although bacteria play a role in its development. It is not unusual for some women to develop acne in their mid- to late-20s.