Doctors often prescribe antibiotics to treat severe acne or acne that is likely to leave scars. Antibiotics improve the look of your skin by killing bacteria that cause acne. This means you'll have fewer pimples and redness. Less acne means less acne scarring.

You can apply antibiotics directly to your skin (topically) or take them by mouth (orally). Topical antibiotics kill bacteria on your skin. Oral antibiotics kill bacteria in your skin pores. Oral antibiotics work best if you start them at high doses. Your doctor will reduce the dose as your acne gets better.

People with mild acne may need only topical antibiotics. The most common types include:

• Erythromycin (E-Mycin).
• Clindamycin hydrochloride (Cleocin).
• Sulfacetamide (Klaron Lotion, Novacet, Sulfacet-R).

In rare cases, topical antibiotics can irritate the skin. Be aware that you may have an allergic reaction to a sulfacetamide lotion if you are allergic to sulfur-based medications.

Talk with your doctor before using these medications if you are pregnant or breast-feeding.

People with severe acne and people who are more likely to have scarring from acne often take antibiotics by mouth. The most common oral antibiotics include:

• Tetracycline hydrochloride (Achromycin).
• Erythromycin (E-Mycin).
• Doxycycline (Vibramycin, Monodox).
• Minocycline hydrochloride (Minocin).
• Trimethoprim-sulfamethoxazole (Bactrim, Septra).
• Amoxicillin (Amoxil).

Over time, bacteria can become resistant to antibiotics. When this happens, the drugs are no longer effective at killing or controlling the bacteria causing the acne. This is called drug resistance. When this occurs, your doctor may give you a different antibiotic. For example, your doctor may give you oral doxycycline when oral erythromycin no longer works on your acne.

To prevent antibiotic resistance, doctors suggest that:

• You try topical medications before taking oral antibiotics.
• You take antibiotics for no longer than is necessary.
• If you need treatment at a later time, you take the same antibiotic that you had before.

For more information on antibiotics, see Drug Reference. (Drug Reference is not available in all systems.)