Common Dog Illnesses: Symptoms, Causes, and When to See a Vet
From kennel cough to kidney disease, this guide covers the most common illnesses dogs face – with clear descriptions of symptoms, what causes each condition, how it is treated, and exactly when to call your veterinarian.
The Most Common Dog Illnesses at a Glance
Dogs are susceptible to a wide range of illnesses, from minor conditions that resolve on their own to serious diseases requiring immediate veterinary attention. Knowing how to recognize common dog illnesses – and understanding the urgency of each – can save your dog’s life.
Respiratory Illnesses in Dogs
Kennel cough
Kennel cough is the most common infectious respiratory disease in dogs. It is caused by a combination of bacteria and viruses, most importantly Bordetella bronchiseptica and canine parainfluenza virus. The hallmark symptom is a harsh, honking cough that sounds like the dog has something stuck in its throat. Despite the dramatic sound, most healthy adult dogs recover within 2 to 3 weeks.
Treatment depends on severity. Mild cases may need only rest and time. Moderate cases benefit from antibiotics (doxycycline is commonly prescribed) to prevent secondary bacterial infection. Severe cases, or those in vulnerable dogs such as puppies or seniors, may require additional supportive care. The kennel cough vaccine reduces risk and severity but does not provide complete protection.
Canine influenza
Canine influenza (dog flu) is caused by two strains: H3N8 and H3N2. Symptoms are similar to kennel cough but often more severe, including a soft moist cough, nasal discharge, fever, and lethargy that can last 2 to 3 weeks. Most dogs recover without complications, but the infection can progress to pneumonia in vulnerable individuals. A vaccine is available for dogs at high risk of exposure.
Pneumonia
Pneumonia in dogs is a serious lung infection that goes beyond simple airway inflammation. Symptoms include a persistent productive cough, labored breathing, fever, and significant lethargy. Dogs with pneumonia require prompt antibiotic treatment and, in severe cases, hospitalization with oxygen supplementation. Any dog with labored breathing should be seen urgently.
Gastrointestinal Illnesses in Dogs
Parvovirus
Canine parvovirus is one of the most serious dog illnesses and is a leading cause of death in unvaccinated puppies. The virus attacks the lining of the gastrointestinal tract, causing severe hemorrhagic diarrhea, vomiting, dehydration, and secondary bacterial infection. Without treatment, mortality rates exceed 90%. With aggressive hospitalization, survival rates can reach 85 to 95%. Parvovirus is prevented by the core vaccine series started at 6 to 8 weeks of age.
Any unvaccinated puppy or dog showing sudden severe vomiting, bloody diarrhea, and collapse must be seen at an emergency vet immediately. Parvovirus kills within days and every hour of delay reduces the chance of survival. If you cannot afford full hospitalization, discuss payment plans or limited treatment options with your vet – something is almost always better than nothing.
Gastroenteritis
Gastroenteritis (stomach and intestinal inflammation) is extremely common and can result from dietary indiscretion (eating something inappropriate), bacterial or viral infection, parasites, or dietary change. Most cases resolve within 24 to 48 hours with rest, a bland diet, and adequate hydration. Seek veterinary care if vomiting or diarrhea persists beyond 24 hours, if blood is present, if the dog shows signs of significant dehydration (sunken eyes, dry gums, skin that does not spring back when gently pinched), or if the dog appears very unwell.
Gastric dilatation-volvulus (bloat)
Bloat is a true surgical emergency in which the stomach fills with gas and twists on itself, cutting off blood supply. It occurs most commonly in large, deep-chested breeds such as Great Danes, German Shepherds, Standard Poodles, and Labrador Retrievers. The stomach twists within minutes, causing shock and death within hours without surgery. Never wait to see if bloat resolves on its own. Any large-breed dog showing abdominal distension, unproductive retching, and restlessness needs emergency care immediately.
Intestinal parasites
Roundworms, hookworms, whipworms, and tapeworms are among the most common internal parasites in dogs. Many dogs carry intestinal worms without obvious symptoms. When present, symptoms include weight loss despite good appetite, a pot-bellied appearance (especially in puppies), diarrhea, visible worm segments in feces or around the tail area, and scooting. Regular fecal testing (at least annually) and appropriate deworming are the best prevention and treatment strategies.
Skin and Ear Illnesses in Dogs
Ear infections
Ear infections (otitis externa) are among the most commonly diagnosed dog conditions, particularly in breeds with long, floppy ears (Cocker Spaniels, Basset Hounds, Beagles) or heavy hair growth inside the ear canal. The warm, moist environment inside a floppy ear creates ideal conditions for yeast and bacteria to proliferate. Signs include head shaking, scratching at the ear, a dark waxy discharge, odor, and redness or swelling of the ear canal. Treatment depends on whether the cause is bacterial, yeast, or both, and requires appropriate ear medication plus treatment of any underlying allergy that predisposes the dog to recurrent infections.
Skin allergies (atopic dermatitis)
Atopic dermatitis is a chronic inflammatory skin condition triggered by environmental allergens such as dust mites, pollen, mold, and certain grasses. It is one of the most common long-term conditions in dogs, particularly in Labrador Retrievers, Golden Retrievers, West Highland White Terriers, Boxers, and Bulldogs. Symptoms include itching (especially around the face, paws, groin, and armpits), recurring ear infections, and recurrent skin infections. Management involves allergen avoidance, medicated shampoos, omega-3 supplementation, and medications such as Apoquel, Cytopoint, or cyclosporine.
Hot spots (acute moist dermatitis)
Hot spots are areas of intensely inflamed, infected skin that develop rapidly – sometimes within hours. They are caused by the dog licking, scratching, or chewing at a site of irritation, creating a moist environment where bacteria multiply rapidly. They appear as red, moist, oozing patches that are intensely itchy and painful. Treatment involves clipping the hair around the lesion, cleaning with an antiseptic, applying topical medication, and preventing the dog from accessing the area with an Elizabethan collar.
Joint and Musculoskeletal Illnesses
Osteoarthritis
Osteoarthritis is the most common joint disease in dogs and is estimated to affect one in five dogs over the age of one year. It involves the progressive degeneration of joint cartilage, leading to pain, stiffness, and reduced mobility. Common signs include difficulty rising from rest, reluctance to climb stairs or jump, lameness that worsens in cold or damp weather, and loss of muscle mass over affected limbs.
Management is multimodal and includes weight management (the single most effective intervention), veterinary NSAIDs for pain relief, joint supplements (omega-3 fatty acids, glucosamine, chondroitin), physiotherapy, controlled exercise, and environmental modifications such as ramps and orthopedic bedding. Emerging treatments include anti-nerve growth factor antibodies (bedinvetmab) which target pain at its source.
Dental Disease
Periodontal disease is estimated to affect more than 80% of dogs over the age of three. It begins with plaque accumulation on tooth surfaces, progresses to tartar formation, and eventually causes gingivitis, bone loss, tooth root infection, and tooth loss. Beyond the mouth, severe dental disease has been linked to heart, kidney, and liver damage from bacteria entering the bloodstream.
Prevention through daily toothbrushing is the gold standard. Dental chews, water additives, and dental diets provide lesser degrees of plaque control. Professional dental cleaning under general anesthesia is required once tartar has mineralized, as it cannot be removed by brushing alone. The frequency depends on the individual dog’s mouth, breed, and home dental care.
Endocrine and Metabolic Illnesses
Hypothyroidism
Hypothyroidism (underactive thyroid) is common in middle-aged to senior dogs, particularly in Golden Retrievers, Dobermans, Irish Setters, and Boxers. The thyroid gland produces insufficient thyroid hormone, resulting in weight gain despite normal or reduced appetite, lethargy, skin and coat changes (dry coat, hair loss, thickened skin), cold intolerance, and slowed heart rate. Diagnosis is by blood thyroid panel. Treatment is daily oral thyroid hormone supplementation (levothyroxine), which must be continued for life.
Cushing’s disease (hyperadrenocorticism)
Cushing’s disease occurs when the adrenal glands produce excessive cortisol, usually due to a pituitary tumor. Classic signs include increased thirst and urination, increased appetite, pot-bellied appearance, muscle weakness, hair loss in a symmetrical pattern, and skin thinning. It is most common in middle-aged to older dogs and breeds such as Poodles, Dachshunds, Boxers, and Beagles. Treatment depends on the cause and may involve medication (trilostane or mitotane) or surgery.
Many common dog illnesses are prevented or caught earlier through regular veterinary check-ups. Annual wellness exams for dogs under 7 years, and twice-yearly exams for seniors, allow your vet to spot early disease before symptoms are obvious. Many conditions are dramatically less expensive and more successfully treated when caught early.
When to Go to the Emergency Vet
The following signs in any dog require immediate emergency veterinary care – do not wait for a morning appointment:
- Difficulty breathing, open-mouth breathing at rest, or blue/grey gums
- Collapse or inability to stand
- Abdominal bloating with unproductive retching (possible bloat)
- Suspected ingestion of toxins (medications, rat poison, xylitol, grapes, chocolate in large amounts)
- Uncontrolled bleeding
- Seizure lasting more than 2 to 3 minutes, or multiple seizures in 24 hours
- Suspected spinal injury or sudden paralysis
- Eye injury or sudden loss of vision
- Urinary obstruction (straining to urinate, crying in pain, producing no urine)
Frequently Asked Questions
Know the Signs, Act at the Right Time
Understanding the most common dog illnesses helps you recognize problems early and respond appropriately – whether that means monitoring at home, booking a routine appointment, or heading straight to emergency care. When in doubt, always contact your veterinarian. Early intervention makes almost every dog illness easier and less expensive to treat.