Fleas are blood-feeding parasites that can infest many species of birds and mammals. Although fleas on dogs and cats don’t infest people, fleas may bite people if an area is heavily infested. Flea infestation is one of the most common medical problems veterinarians see, and pets suffer greatly from this condition. Flea bites can trigger severe allergic reactions in some pets. The intense itching caused by flea infestation causes pets to scratch and bite themselves. This can lead to skin wounds, skin infections, and general misery for your pet. Even if your pet is not allergic to flea bites, fleas can transmit serious diseases, such as bartonellosis (the bacteria that causes “cat scratch disease” in people), and other parasites, like tapeworms.

The most common types of allergies in pets are flea allergy, food allergy, and a condition called atopy. Atopy is sometimes called atopic dermatitis or allergic inhalant dermatitis, and it occurs when allergens that are inhaled or that contact the skin cause an allergic reaction in the body. In dogs (and, less commonly, cats), this allergic reaction is focused largely in the skin. Animals with atopy become very itchy; the resultant scratching can lead to skin injuries and subsequent skin infections. Atopy is usually first noticed in dogs younger than 3 years of age, although older pets can also be affected. Unfortunately, some pets that develop atopy continue to have problems throughout their lives.  

Some animals may have several of these clinical signs, whereas others may have only one—perhaps an ear infection.

Bee stings can be a serious event and even life threatening in some cases. Dogs are at greater risk for bee stings than people, as they tend to chase or play with things that move. Dogs are likely to get stung in the mouth or on the nose, face, or feet by several different insects, including bees, wasps, and hornets.

Heartworm disease is a serious and potentially fatal condition that affects dogs, cats, and up to 30 other species of animals. It is caused by parasitic worms (heartworms) living in the major blood vessels of the lungs and, occasionally, in the heart. These worms are transmitted (as microscopic larvae) through the bite of an infected mosquito. The scientific name for the heartworm parasite is Dirofilaria immitis.