Ten years ago, Shirley Worthington rushed Tigger to the vet when the dog's mouth started bleeding. When she was told he had cancer, she knew to blame her heavy smoking, she couldn't kick until after her pet died.

Secondhand smoke can cause lung and nasal cancer in dogs, malignant lymphoma in cats and allergy and respiratory problems in both animals, according to studies done at Tufts University's School of Veterinary Medicine in Massachusetts, Colorado State University and other schools.

The number of pets that die each year from tobacco exposture isn't available, but vets know from lab tests and office visits that inhaling smoke causes allergic reactions, inflammation and nasal and pulmonary cacers in pets, said Dr Kerri Marshall, the chief veterinary officer for Trupanion pet insurance.

Symptoms of cancer in animals include coughing, trouble eating or breathing, drooling, weight loss, vomiting, nasal discharge, bleeding and sneezing. Cancer kills more dogs and cats than any other disease, according to Denver-based Morris Animal Foundation, which has been funding pet cancer research since 1062.

In addition, the recent surge in the use of electronic cigarettes has raised questions about their impact on pets. The greatest danger is the trash, where dogs can find nicotine cartridges from e-cigarettes.