Dogs get their noses into everything. They can sniff out where you’ve hidden the treats, they know you’ve been petting the dog next door (you cheater), and they greet your guests by shoving their noses into their privates.


Dogs even have jobs as master sniffers: Illegal drugs, explosives, missing humans – if it has a smell, dogs can be trained to hone in on it more accurately than other detection methods. And now we’re training dogs to find cancer.


But don’t run out to a dog park for your next cancer screening. “We don’t ever anticipate our dogs walking through a clinic,” says veterinarian Dr. Cindy Otto of the Penn Vet Working Dog Center, where dogs like McBaine the Springer Spaniel are trained to detect cancer using their highly sensitive noses.


Trainers have the talented pups sniff two vials of fluid, one cancerous and one benign. “Everything we do is about positive reinforcement,” Dr. Otto said. “Sniff the right odor, earn a toy or treat. It’s all one big game,” said Dr. Otto.


We still don’t know what it is exactly that these dogs are picking up when they smell cancer. The goal is to pinpoint the chemical marker the dogs have been smelling, which will then help scientists create a handy sensor used for detecting cancer present in the body. And since early detection of cancer is one of the most important parts of successful treatment, figuring this out will be a huge breakthrough in the field.