Although symptoms of illness in puppies vary depending on the disease, they commonly include vomiting, lethargy, change in appetite, excessive drooling and skin irritation. Sick puppies often have a fever, but that can be difficult to notice at first.
One of the most common symptoms is a sudden change in appetite, especially a refusal to eat. Drinking excessive amounts of water leading to frequent urination is another sign that something is wrong. Sick puppies may seem tired and listless, but extreme restlessness is also a sign of discomfort. Any sudden change in behavior can be a sign of illness.
Digestive upset, such as diarrhea or vomiting, happen occasionally to most puppies, but severe or long-lasting cases mean that something is wrong. Sneezing, coughing and gagging are sometimes present when a puppy is ill. Labored breathing or a runny nose are common symptoms of respiratory illnesses.
Sudden weight changes are another symptom. Some weight fluctuation is normal in growing puppies, but major changes that do not seem to match food consumption are sometimes a sign of underlying illness, even if the puppy seems normal otherwise.
Dry, flaky skin or skin that is red or irritated may indicate illness or allergies. Although it is uncommon in young puppies, red swollen gums and drooling can indicate dental problems or gum disease. Filmy or runny eyes also need to be seen by a veterinarian.