Family pets are equally, if not more, at risk of being affected by passive smoking as humans, research suggests.
Animals inhale more smoke and - because of their grooming routines - also digest nicotine when licking their fur, a study by Glasgow University said.
Dogs are at risk of developing lung or sinus cancer while smaller pets such as birds, rabbits and guinea pigs can face breathing issues and skin disease.
Experts hope the findings will motivate pet owners to quit smoking.
The Royal College of Veterinary Surgeons has teamed up with The Royal College of Nursing for a new campaign aimed at telling owners about the damage that can be done.
Wendy Preston, the RCN's Head of Nursing, said: "Many people would be horrified to discover their second-hand smoke was harming their pet, and in some cases seriously shortening the animal's life.
"We want to make it easier for vets and vet nurses to have that conversation with patients."
Simon Clark, director of the smokers' group Forest, said he felt the threat of passive smoking on animals was "greatly exaggerated". He also said it was a distraction from genuine cases of animal abuse.
What are the risks?
- Dogs can develop lung or sinus cancer
- Cats have an increased risk of developing lymphoma
- Birds, rabbits and guinea pigs can suffer eye, skin and respiratory disease
- Smoke exposure worsens bronchitis and asthma in animals that already have those conditions
Source: Royal College of Nurses
The university, which is renowned for its small animal hospital, has been carrying out research on the effects of passive smoking on pets for several years,
Professor Clare Knottenbelt said 40 dogs - half of them from homes with smokers - were recruited for the study and samples of their hair were analysed for nicotine levels, while their owners were asked to fill in a survey detailing how often they or any visitors smoked.
The same study was then carried out on 60 pet cats, with a particular focus on whether any link could be established between second-hand smoke and feline lymphoma, a cancer that affects the white blood cells of cats.
But she said that the researchers had to factor in the very different behaviour of cats and dogs, pointing out that free-wandering cats could potentially be exposed to second hand smoke if they visit other people's homes and even sit close to pub or workplace entrances where groups of smokers congregate.
She said: "A cat can be from a smoke-free home yet still have high nicotine levels."
But Forest's Simon Clark was dismissive of the research, saying: "The best thing anyone can do for their pets is provide a warm, comfortable environment where they feel safe and cared for."