Cephalexin: What It Is, How It Works, and What Alternatives Exist

When you have a bacterial infection—whether it’s a skin rash, a sinus infection, or a urinary tract issue—your doctor might prescribe cephalexin, a first-generation cephalosporin antibiotic used to treat common bacterial infections. Also known as Keflex, it’s one of the most widely used oral antibiotics because it’s effective, affordable, and generally well-tolerated. Unlike some stronger antibiotics, cephalexin doesn’t cover every type of bacteria, but it’s a solid first-line choice for many everyday infections like strep throat, cellulitis, and ear infections.

It works by stopping bacteria from building their cell walls, which causes them to burst and die. This makes it a beta-lactam antibiotic, a class of drugs that includes penicillins and other cephalosporins, and that’s why people allergic to penicillin should be cautious—cross-reactivity can happen. If you’ve had a reaction to amoxicillin or penicillin before, talk to your doctor before taking cephalexin. It’s not a cure-all, and it won’t help with viruses like the flu or a cold. Using it when it’s not needed can lead to resistance, which is why it’s important to take the full course, even if you feel better after a few days.

Many people wonder how cephalexin stacks up against other options. amoxicillin, a penicillin-based antibiotic often used for similar infections is a common alternative. Some studies show they’re equally effective for ear infections and skin infections, but amoxicillin might be preferred for respiratory infections because it covers a slightly broader range of bacteria. Then there’s clindamycin, an option for people who can’t take beta-lactams, often used for stubborn skin infections or when resistance is a concern. Cephalexin is usually cheaper than newer antibiotics and has fewer side effects than some alternatives, like fluoroquinolones, which can cause tendon issues or nerve damage.

Side effects are usually mild—stomach upset, diarrhea, or a rash—but if you develop severe diarrhea, swelling, or trouble breathing, stop taking it and get help right away. It’s also worth noting that cephalexin can affect how some other drugs work, especially probenecid or metformin, so always tell your doctor what else you’re taking. If you’re pregnant, breastfeeding, or have kidney problems, your dose might need adjusting.

What you’ll find below is a collection of detailed comparisons between cephalexin and other common treatments—some direct, some indirect. You’ll see how it compares to other antibiotics used for skin infections, how it stacks up against alternatives for urinary tract infections, and why some people switch from one drug to another. There are also posts on how to avoid common mistakes when taking antibiotics, how to recognize signs of resistance, and what to do if your infection doesn’t improve. This isn’t just a list of articles—it’s a practical guide to making smarter choices about your treatment.