Impetigo and Cellulitis: How to Choose the Right Antibiotics for Skin Infections

Two of the most common skin infections you’ll hear about in clinics, schools, and emergency rooms are impetigo and cellulitis. They look similar at first glance-red, irritated skin-but they’re not the same. One is mostly a surface problem, often seen in kids. The other digs deep, can turn dangerous fast, and demands serious attention. Getting the right antibiotic isn’t just about following a script-it’s about matching the drug to the bug, the location, and the risk.

What Impetigo Really Looks Like

Impetigo doesn’t start with a big wound. It starts with a tiny scratch, a mosquito bite, or even a patch of eczema that’s been scratched raw. Within a day or two, small red sores appear, usually around the nose and mouth, but also on arms and legs. These sores burst quickly, leaving behind a sticky, honey-colored crust. That’s the classic sign of nonbullous impetigo-the most common type, making up about 70% of cases.

The other form, bullous impetigo, is less common. It shows up as larger blisters filled with clear or yellow fluid. These blisters are fragile. When they pop, they leave behind a ring-like border, like a tiny donut of dried skin. Both types are caused by Staphylococcus aureus or Streptococcus pyogenes. Kids between 2 and 5 are most at risk. It spreads like wildfire in daycare centers and classrooms. One child with impetigo can infect half a class within a week if no one notices.

Cellulitis: When the Infection Goes Deep

Cellulitis is a different beast. It doesn’t form crusts or blisters. Instead, the skin becomes hot, swollen, tight, and painfully tender. The redness doesn’t have clean edges-it bleeds outward, like ink dropped in water. It often shows up on the lower legs, but can appear anywhere: arms, face, even around the eyes. Unlike impetigo, which stays on top, cellulitis invades the dermis and fat layer beneath. That’s why it can cause fever, chills, or swollen lymph nodes. If it’s not treated, it can spread to the bloodstream and cause sepsis.

It’s not just a skin problem. People with diabetes, poor circulation, or weakened immune systems are at higher risk. Even a small cut from gardening or a pet scratch can become a portal. Erysipelas, a related condition, looks like cellulitis but has sharp, raised borders and is almost always caused by Streptococcus. Doctors often treat them the same way, but the sharp edge is a clue.

Antibiotic Choices: Why One Size Doesn’t Fit All

You might think, “Just give an antibiotic and it’s done.” But the choice matters-big time. The wrong one can fail, or worse, make resistance worse.

For impetigo, if it’s limited to a few spots, topical mupirocin works well. It’s applied directly to the skin three times a day for 7 to 10 days. Studies show it clears up about 90% of cases. But if the infection is widespread, or if the person has a fever, oral antibiotics are needed. In the UK and Belgium, flucloxacillin is the go-to. In France, doctors often start with amoxicillin-clavulanate or pristinamycin. Why the difference? Because resistance patterns vary by country. In places where MRSA is common, flucloxacillin won’t work. That’s why cultures are becoming more common in stubborn cases.

For cellulitis, oral antibiotics are almost always required. First-line choices depend on where you live. In the UK, flucloxacillin is standard. In France, amoxicillin is increasingly used. Both target Streptococcus, which causes most cases. But if there’s a history of MRSA-like a recent hospital stay, a history of skin abscesses, or living in a community with high MRSA rates-doctors switch to clindamycin or trimethoprim-sulfamethoxazole. Vancomycin is reserved for severe cases that need hospitalization.

MRSA: The Silent Game-Changer

MRSA-methicillin-resistant Staphylococcus aureus-has changed everything. It doesn’t respond to penicillin, amoxicillin, or flucloxacillin. And it’s no longer just a hospital problem. In many U.S. communities, over 40% of skin infections caused by staph are MRSA. That means if you’ve had a skin infection before that didn’t get better with a standard antibiotic, you might be carrying it.

Doctors now ask: “Have you had a skin abscess? Been in the hospital? Had a roommate with a similar infection?” If yes, they skip flucloxacillin and go straight to something that covers MRSA. Culture and sensitivity tests are now used in 65% of recurrent or treatment-resistant cases. That’s a big shift from just 10 years ago, when antibiotics were often prescribed without testing.

How Long Do You Really Need to Take Them?

Most people think: “I feel better, so I’ll stop.” That’s dangerous. Stopping early is one of the top reasons antibiotics stop working.

For impetigo, 7 to 10 days is standard-even if the crusts are gone by day 3. For cellulitis, the course is usually 5 to 14 days, depending on how bad it was. If you’re hospitalized, you might start with IV antibiotics, then switch to pills once you’re stable. The rule? Don’t stop until the full course is done. Even if the redness fades, bacteria can still be hiding under the skin.

What Happens If You Wait Too Long?

Delaying treatment by more than 48 to 72 hours increases the risk of complications. With impetigo, the infection can spread to other parts of the body or cause kidney inflammation (post-streptococcal glomerulonephritis)-rare, but serious. With cellulitis, the risks are immediate: abscesses, necrotizing fasciitis (flesh-eating bacteria), or sepsis. One study showed that patients who waited more than 3 days to see a doctor were 3 times more likely to need hospitalization.

Prevention: Simple Steps That Make a Big Difference

You can’t always avoid infection, but you can cut your risk way down.

- Wash cuts and scrapes with soap and water right away. Don’t let them dry out. Cover them with a bandage.

- Never share towels, razors, or clothing. Impetigo spreads through contact with contaminated items.

- Keep fingernails short, especially in kids. Scratching spreads bacteria.

- If someone in the house has impetigo, wash bedding and clothes daily in hot water.

- For people with diabetes or poor circulation, check feet and legs daily for redness, swelling, or breaks in the skin.

When to See a Doctor

You don’t need to rush to the ER for every red spot. But call your doctor if:

- The red area is spreading fast (more than 1 inch in 24 hours)

- You have a fever, chills, or feel dizzy

- The skin feels hard or numb

- You’ve had this before and it came back

- The infection is on your face, near your eyes, or on a child under 2

- Over-the-counter creams or home care haven’t helped in 2 days

Antibiotic Stewardship: Why We Can’t Just Keep Prescribing

Doctors are under pressure to prescribe antibiotics quickly. But overuse is making them less effective. In the U.S., 20-30% of skin infection prescriptions are unnecessary. That’s why experts now push for “antibiotic stewardship”-using the narrowest, most targeted drug possible.

Instead of grabbing amoxicillin or cephalexin for every red patch, doctors are learning to ask: “Is this likely staph? Streptococcus? MRSA?” They’re using local resistance data, patient history, and sometimes rapid tests to choose better. The goal? Cut unnecessary prescriptions by 40% in the next five years. That’s not just about saving money-it’s about saving lives.

What Comes Next?

The future of treating these infections is moving toward smarter, faster decisions. New rapid tests can identify staph vs. strep-and even detect MRSA-in under an hour. That means doctors won’t have to guess anymore. They’ll know exactly what to prescribe from day one.

In the meantime, the best thing you can do is act fast. If you see redness spreading, heat, or pain that’s getting worse-don’t wait. Don’t assume it’s just a rash. See a doctor within 48 hours. Early treatment saves skin, saves time, and saves lives.