Most infections in dogs require prescription antibiotics from a veterinarian. As of 2024, all medically important antimicrobials for animals in the United States require a veterinary prescription, so there is no effective over-the-counter antibiotic you can buy for your dog. That said, some mild skin infections can be managed at home with topical antiseptics, and knowing what vets typically prescribe helps you understand what to expect at your appointment.
Why You Can’t Buy Dog Antibiotics Over the Counter
The FDA completed a transition moving all medically important antimicrobial drugs for animals from over-the-counter to prescription-only status. Once remaining OTC-labeled inventory depleted from store shelves, every antibiotic that works against serious infections became available only through a licensed veterinarian. This change was driven by growing antibiotic resistance, and it means products like fish antibiotics or livestock penicillin that some pet owners previously used are no longer legally sold without a prescription.
What Veterinarians Typically Prescribe
The specific antibiotic your vet chooses depends on where the infection is and what type of bacteria is involved. Based on prescribing patterns at veterinary teaching hospitals, the most commonly used antibiotics for dogs fall into a few categories.
Amoxicillin-clavulanate is the single most frequently prescribed antibiotic for dogs. It’s a broad-spectrum drug that’s relatively inexpensive and causes few side effects, making it a common first choice for skin wounds, urinary tract infections, and respiratory infections. Cephalexin is the second most common, often used for skin infections, wounds, and abscesses. It covers a narrower range of bacteria, which veterinary organizations actually prefer because narrow-spectrum drugs are less likely to fuel antibiotic resistance. Enrofloxacin tends to be reserved for more serious or mixed infections and is the antibiotic most frequently backed by a positive culture result, meaning vets often confirm the specific bacteria before reaching for it. Doxycycline rounds out the top five and is commonly used for tick-borne diseases like Lyme disease and ehrlichiosis.
Your vet may take a sample for bacterial culture before prescribing, especially if the infection is severe or has come back after a previous round of treatment. Culture and sensitivity testing at a diagnostic lab typically costs around $35 to $55, plus roughly $48 for a cytology exam if one is needed. These tests identify exactly which bacteria are present and which drugs will kill them, preventing wasted time on the wrong antibiotic.
Topical Treatments You Can Use at Home
For surface-level skin infections, topical antiseptics are the recommended first-line treatment, and some are available without a prescription. International veterinary dermatology guidelines specifically state that topical therapy alone is the treatment of choice for surface and superficial skin infections in dogs, and that antiseptics should be prioritized over topical antibiotics.
Chlorhexidine is the go-to ingredient. Medicated shampoos containing 2% to 4% chlorhexidine work well for widespread skin issues like hot spots or mild bacterial skin infections (pyoderma). The key is contact time: lather the shampoo onto the affected area and leave it on for 10 to 15 minutes before rinsing. For initial treatment, plan on bathing two to three times per week. For smaller, localized patches, chlorhexidine sprays or wipes applied once daily are more practical. Benzoyl peroxide shampoo at 2.5% is another option, particularly for folliculitis where bacteria get trapped in hair follicles.
Creams and gels work best for infections in skin folds, around the lips, or in other hard-to-reach spots. These are typically applied once or twice daily and left on without rinsing. If your dog’s skin infection involves deep lesions, spreading redness, or hasn’t improved after a week of topical care, oral antibiotics from your vet will likely be needed.
Eye and Ear Infections Need Specific Drops
Eye infections in dogs are not something to treat with general-purpose products. Veterinary eye drops contain specific antibiotic combinations, with triple antibiotic preparations (neomycin-polymyxin-bacitracin) being a common starting point for uncomplicated infections or corneal ulcers. For more resistant infections, your vet may prescribe fluoroquinolone drops or aminoglycoside drops. If your dog needs multiple eye medications, separate each drop by at least five minutes so the first medication isn’t washed out by the second.
Ear infections are similar in that they require diagnosis before treatment. What looks like a bacterial ear infection could be fungal, or it could involve a ruptured eardrum that makes certain medications dangerous. Your vet will look inside the ear canal with an otoscope before choosing the right medicated drops.
Common Infection Types to Watch For
Skin infections are by far the most common reason dogs end up on antibiotics. They often start as small red bumps, crusty patches, or hair loss and can escalate quickly if a dog keeps scratching or licking. Urinary tract infections are another frequent culprit, showing up as frequent urination, straining, accidents in the house, or blood-tinged urine. Wound infections from cuts, bites, or surgical sites are also common and tend to produce swelling, discharge, and warmth around the area.
Some bacterial infections carry higher stakes. Leptospirosis, for example, is a bacterial disease dogs can pick up from contaminated water or wildlife urine. It causes fever, vomiting, diarrhea, increased thirst, lethargy, and muscle stiffness. In severe cases, it can lead to jaundice (yellowing of the eyes and gums), tiny bleeding spots under the skin, and even bleeding into the lungs. Leptospirosis is also transmissible to humans, making prompt veterinary treatment essential.
Signs an Infection Is an Emergency
Not every infection warrants a rush to the emergency vet, but certain signs indicate your dog may be going into sepsis or shock and needs immediate care. Check your dog’s gums: healthy gums are pink and moist. Pale or white gums suggest anemia or shock. Gums that look bluish, gray, or muddy-colored indicate dangerously low oxygen levels. Yellow gums point to liver involvement or red blood cell destruction. Any of these color changes in a dog that’s also lethargic, refusing food, or running a fever is a true emergency.
Other red flags include labored open-mouth breathing, extreme weakness or collapse, and tiny red or purple spots on the skin or gums (petechiae), which can signal a clotting problem. If your dog is vomiting repeatedly, has bloody diarrhea, or seems disoriented, don’t wait to see if things improve overnight.
How Long Treatment Typically Lasts
Antibiotic courses for dogs vary widely depending on the infection. A straightforward urinary tract infection might need 7 to 14 days of medication, while a deep skin infection could require 4 to 6 weeks or longer. Veterinary stewardship guidelines emphasize using the shortest effective course to get the job done while minimizing resistance, so your vet will tailor the duration to your dog’s specific situation.
The most important thing you can do is finish the entire prescribed course, even if your dog looks and acts completely normal before the pills run out. Stopping early is one of the main drivers of resistant infections that become harder and more expensive to treat the second time around. If your dog is having side effects like vomiting or diarrhea from the medication, call your vet about adjusting the approach rather than simply stopping.