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

Two skin infections you’ve probably heard of - impetigo and cellulitis - look similar at first glance. Both cause red, irritated skin. Both can spread quickly. And both need antibiotics. But they’re not the same. Mixing them up can mean wrong treatment, longer illness, or worse complications.

What Impetigo Really Looks Like

Impetigo is the classic "school sore." It’s most common in kids between ages 2 and 5, but adults can get it too - especially if they have eczema, a cut, or a bug bite. It starts as tiny red spots, often around the nose or mouth. Within hours, those spots turn into blisters that pop, leaving behind a sticky, honey-colored crust. That’s the hallmark.

There are two types. Nonbullous impetigo makes up about 70% of cases. It’s the crusty kind. The other, bullous impetigo, shows up as larger, fluid-filled blisters (2-5 cm wide) that burst easily. After they break, you’ll see a ring of leftover skin around the raw area. It’s less common but more dramatic-looking.

The bacteria behind it? Mostly Staphylococcus aureus, sometimes Streptococcus pyogenes. These bugs don’t always need broken skin to invade. Sometimes they just crawl onto healthy skin and start multiplying. That’s why it spreads so fast in daycare centers and classrooms. One child scratching their nose, then touching a toy - and suddenly half the class has it.

Cellulitis Is Deeper - and More Dangerous

Cellulitis doesn’t just sit on the surface. It digs into the dermis and fatty tissue underneath. You won’t see honey-colored crusts. Instead, the skin turns bright red, swells up, feels hot to the touch, and hurts when you press it. The edges are blurry - not sharp like in erysipelas (a related condition caused mostly by Streptococcus).

It often starts at a wound: a scrape, a bite, a fungal infection between the toes, or even a cracked heel. But it can also appear out of nowhere, especially in people with diabetes, poor circulation, or a weak immune system. Older adults and those with swollen legs from venous insufficiency are at higher risk.

Unlike impetigo, cellulitis can make you feel sick. Fever, chills, and fatigue often come with it. If it spreads, it can lead to sepsis - a life-threatening response where your body goes into overdrive trying to fight the infection. That’s why it’s not something to wait on.

Antibiotic Choices: UK vs. France vs. Belgium

Here’s where things get messy. There’s no single global rule. What works in Bristol might be unusual in Paris or Brussels.

In the UK, flucloxacillin is the go-to for both impetigo and cellulitis. It’s a penicillin-type antibiotic that kills Staphylococcus, including the common strains. Doctors here start with oral flucloxacillin for 7-10 days. For more serious cellulitis, they might switch to IV in hospital.

In France, doctors lean toward amoxicillin for cellulitis. For impetigo, they often use pristinamycin or amoxicillin-clavulanate. Why? Because resistance patterns differ. In some parts of Europe, Staphylococcus is less likely to resist amoxicillin-based drugs than in the UK.

Belgium doesn’t have national guidelines. Doctors there mostly follow what’s worked locally - and that’s often flucloxacillin, too.

The key takeaway? Location matters. Your doctor doesn’t just pick a drug because it’s "standard." They pick it based on what’s working - and what’s failing - in your area.

When MRSA Changes Everything

Not all staph is the same. MRSA - methicillin-resistant Staphylococcus aureus - doesn’t respond to flucloxacillin, amoxicillin, or any penicillin-based drug. It’s become more common in community settings, not just hospitals.

If you’ve had a skin infection before that didn’t improve with standard antibiotics, or if you’ve been in a hospital recently, your doctor might suspect MRSA. Signs? Rapid worsening, pus-filled boils, or infections that keep coming back.

For MRSA, you need different antibiotics: clindamycin, doxycycline, or in severe cases, vancomycin given intravenously. Culture tests - where they take a swab and grow the bacteria in a lab - are now routine for recurrent or treatment-resistant cases. About 65% of stubborn infections get tested now, compared to just 20% a decade ago.

Topical vs. Oral: What Works for Impetigo

For small, localized impetigo - say, one or two patches on the face - mupirocin ointment is often enough. Applied three times a day for 7-10 days, it clears up 90% of cases. No pills needed.

But if the infection covers a bigger area, or if there are multiple people in the house with it, oral antibiotics are better. Flucloxacillin or cephalexin for 7-10 days. Why? Because topical treatments don’t reach deep enough if the bacteria have spread under the skin.

And here’s a trick: clean the area first. Gently wash the crusts off with soap and water, then pat dry before applying ointment. That helps the medicine stick better.

How Long Until It Gets Better?

You should see improvement within 48 to 72 hours after starting antibiotics. Redness fades. Pain drops. Crusts start to dry up.

If nothing changes after three days - or if it gets worse - call your doctor. You might need a different antibiotic, or the infection could be spreading.

For cellulitis, recovery takes longer. Even with the right drug, it can take 7-14 days to fully clear. You might still feel tired or have mild swelling for weeks after. That’s normal. But if you develop a fever, chills, or the red area keeps growing, get to a hospital fast.

Stopping the Spread: Prevention Tips

Both infections are contagious - but you can stop them.

• Wash hands often - especially after touching infected skin.
• Don’t share towels, clothes, or bedding with someone who has it.
• Cover wounds with clean bandages until they heal.
• If your child has impetigo, keep them home from school or daycare until they’ve been on antibiotics for at least 24 hours.
• Keep fingernails short. Scratching spreads bacteria to other parts of the body.
• If you have eczema or diabetes, treat your skin daily. Dry, cracked skin is a doorway for bacteria.

What Happens If You Ignore It?

Impetigo usually doesn’t cause long-term harm if treated. But left alone, it can spread to other parts of the body or to other people. Rarely, it can lead to kidney problems - a condition called post-streptococcal glomerulonephritis.

Cellulitis? That’s riskier. Untreated, it can spread to the bloodstream (sepsis), bones (osteomyelitis), or even the brain (if near the eyes or sinuses). One study showed that 1 in 10 people with cellulitis had to be hospitalized because it got worse at home.

And here’s the silent cost: recurrent infections. People with chronic cellulitis often miss weeks of work. Some have flare-ups every few months. That’s not just a health issue - it’s a life disruption.

When to See a Doctor

Don’t wait. See a doctor if:

• You see honey-colored crusts - especially on a child.
• Your skin is red, swollen, warm, and painful - and it’s spreading.
• You have a fever along with skin changes.
• You’ve had this before and it’s coming back.
• You have diabetes, heart disease, or a weak immune system.

Even if you think it’s "just a rash," get it checked. Skin infections don’t always look like textbook pictures. Sometimes they start subtle - and explode fast.