Common Dog Illnesses: Signs, Causes & Prevention

Common Dog Illnesses — The Short Answer

Most dog illnesses fall into a few groups: infections (like ear infections and parvo), parasites (like heartworm and ticks), and long-term conditions (like dental disease, diabetes, and cancer). Many of them are preventable or much easier to treat when caught early.

You don't need to memorize a vet textbook. You just need to know which problems are common, what the first signs look like, and when to pick up the phone. If you want a general checklist first, start with our guide on how to tell if your dog is sick.

Everyday Illnesses Vets See Most

Ear infections

VCA Animal Hospitals calls outer ear infections one of the most common infections in dogs. Breeds with floppy or hairy ears, like Cocker Spaniels and Poodles, are more prone.

Allergies play a big role. VCA says allergies are involved in as many as 43% of ear infection cases.

Signs: head shaking, scratching at the ears, a bad smell, and dark or yellow discharge. Skip the home remedies. A vet needs to check what's causing it and whether the eardrum is intact.

Dental disease

Plaque hardens into tartar, which irritates the gums and can lead to infection and tooth loss. It creeps up slowly, so many owners don't notice until it's advanced.

Signs: bad breath, red gums, tartar on the back teeth, dropping food, or chewing on one side. Daily brushing and yearly dental checks make a real difference.

Skin allergies and itching

Itchy skin is a very common complaint, and it can wear a dog down fast. Triggers include fleas, pollen, and sometimes food.

Signs: constant licking or chewing of the paws, red skin, hair loss, and repeated ear infections. If food seems to be the trigger, our guide to dog food for food allergies explains how an elimination diet works.

Stomach upsets

Vomiting and diarrhea often come from eating something they shouldn't have, a sudden food change, or stress. Most mild cases pass in a day.

Signs to take seriously: blood in stool or vomit, repeated vomiting, or a dog who won't drink. Our guide to canine food poisoning covers what to do next.

Infectious Diseases to Vaccinate Against

Parvovirus

Parvo is a serious virus that mostly hits puppies and unvaccinated dogs. According to the AKC, it can survive indoors on surfaces for at least a month and outdoors for months or even a year.

Signs: bloody diarrhea, vomiting, fever, and extreme tiredness, usually 3 to 7 days after exposure. The AKC reports a survival rate of 68 to 90% with treatment, so fast care matters. Puppies need their full vaccine series before visiting dog parks or other high-traffic spots.

Kennel cough

Kennel cough is a contagious airway infection that spreads where dogs gather. The ASPCA describes the classic sign as a persistent, dry, "honking" cough. Most cases are mild, but puppies and older dogs can get sicker.

Rabies

Rabies spreads mainly through bites from infected animals. It is almost always fatal, which is why the vaccine is required by law in many places.

Parasite-Borne Illnesses

Heartworm

Mosquitoes carry heartworm, and the ASPCA notes it has been found in every U.S. state except Alaska. The worms live in the heart and lungs and can cause serious damage before signs appear.

Prevention is simple: a monthly preventive, given all year. The ASPCA points out that the American Heartworm Society recommends year-round use.

Lyme disease

Lyme disease comes from certain ticks. The AKC says a tick usually needs to be attached for 24 to 48 hours to pass it on, so daily tick checks really work.

Signs: lameness that shifts from leg to leg, fever, low energy, and swollen joints. Some infected dogs never show signs at all.

Long-Term Conditions in Adult and Senior Dogs

Obesity

Extra weight isn't just cosmetic. It raises the risk of joint problems, diabetes, and a shorter life. Our dog calorie calculator helps you set portions that fit your dog's actual needs.

Diabetes

The ASPCA lists excessive thirst, frequent urination, weight loss, and cataracts as common signs. It notes that a proper diet and regular exercise can go a long way toward prevention.

Arthritis

Stiffness after rest, slowing down on walks, and trouble with stairs are classic signs. It's common in larger and older dogs, and weight control is one of the best ways to ease it.

Cancer

Cancer is more common as dogs age. Watch for new lumps, sores that don't heal, unexplained weight loss, or changes in breathing. Any new lump deserves a vet check. If your dog is losing weight without trying, our guide to a dog losing weight lays out the next steps.

How to Lower Your Dog's Risk

• Keep vaccines current. Your vet will tailor non-core shots to your dog's lifestyle.
• Use parasite prevention all year. That covers heartworm, fleas, and ticks.
• Brush teeth daily. Even a few times a week helps.
• Keep your dog lean. A visible waist and easy-to-feel ribs are the goal.
• Book regular checkups. Once a year for adults, and often twice a year for seniors. A pet wellness plan can help spread out the cost.
• Know your dog's normal. Appetite, energy, and bathroom habits are your early warning system.

When to Call Your Vet Right Away

Get same-day help for:

• Bloody diarrhea or repeated vomiting
• Trouble breathing or a constant cough
• A swollen, hard belly or unproductive retching
• Collapse, seizures, or sudden weakness
• Not eating or drinking for more than a day
• Any suspected poisoning (see our list of toxic foods for dogs)

If you're unsure, call anyway. Vets would much rather hear from you early.

Practical Takeaways

• Ear infections, dental disease, skin allergies, and stomach upsets are the everyday illnesses most dogs face
• Vaccines protect against parvo, rabies, and other serious infections
• Year-round heartworm and tick prevention stops problems that are hard to treat later
• Weight control lowers the risk of diabetes, arthritis, and more
• Knowing your dog's normal habits is the best early warning you have