Cephalexin vs Amoxicillin: Key Differences and When to Use Each

When your doctor prescribes an antibiotic, you might hear cephalexin, a first-generation cephalosporin antibiotic used for skin, bone, and respiratory infections or amoxicillin, a penicillin-class antibiotic commonly used for ear, sinus, and urinary tract infections. Both fight bacterial infections, but they’re not interchangeable. antibiotic resistance, the growing problem where bacteria evolve to survive drug treatment makes choosing the right one even more critical. Using the wrong one doesn’t just waste time—it can make your infection harder to treat later.

Amoxicillin works best against common bugs like Streptococcus and some E. coli strains, which is why it’s often the first pick for ear infections in kids or strep throat. Cephalexin, on the other hand, is stronger against certain skin infections like cellulitis and can be a go-to if you’re allergic to penicillin—though not always, since some people allergic to penicillin also react to cephalosporins. side effects, the unwanted reactions from taking medication are similar: nausea, diarrhea, and stomach upset. But amoxicillin can cause more rash in people with mononucleosis, while cephalexin is more likely to trigger yeast infections. Neither works against viruses, so if you have a cold or flu, neither will help.

Cost and availability matter too. Both are cheap generics, but amoxicillin is usually the most affordable. If you’ve tried amoxicillin before and it didn’t work, your doctor might switch you to cephalexin—not because it’s "stronger," but because it attacks different bacterial targets. antibiotic spectrum, the range of bacteria a drug can kill is the real deciding factor. One size doesn’t fit all. The posts below break down real cases: when cephalexin beats amoxicillin, when the reverse is true, how allergies affect choice, and why some people get worse side effects on one than the other. You’ll also find comparisons with other antibiotics, what doctors actually say in practice, and how to spot if your infection isn’t responding. No fluff. Just what you need to understand your prescription—and ask the right questions.