Dogs have an incredible sense of smell. In fact, canines are equipped with over 100 million sensory receptors within their nasal cavity, whereas humans possess about six million. Additionally, dogs also have a second olfactory system that not only allows them to pick up on physical smells but also allows them to detect pheromones, human emotions, and even the presence of storms.
Given their powerful noses, it’s no wonder dogs have been used in hunting, trained to sniff out bombs or drugs, and assisted in search and rescue missions.
However, the 10 dogs on this list were able to accurately detect a much more important, typically undetectable odor in their owners—cancer. And they did so long before their human companions were ever diagnosed by a healthcare professional.
Related: Top 10 Dogs With Unusual Jobs
10 Sierra the Siberian Husky
When Stephanie Herfel’s son left for the Air Force in 2011, she took in his nine-month-old Siberian husky puppy, Sierra. Little did Herfel know what a gift Sierra would truly be.
One day in 2013, Sierra began sniffing and pressing her nose into Herfel’s abdomen. At first, Herfel assumed that perhaps the dog smelled food that she had spilled on her shirt. However, the substance Sierra detected was startling enough to make her roll up into a ball and hide in the closet.
While Herfel had previously experienced pain in her abdomen, she was advised by an ER physician that she had an ovarian cyst and was sent home with pain medication. Given Sierra’s reaction, Herfel made an appointment with her gynecologist. On November 11, 2013, her doctor confirmed that she had stage 3 ovarian cancer.
Herfel had a full hysterectomy, lost her spleen, and continued chemotherapy until April 2014. Unfortunately, in 2015, Sierra again exhibited the same behavior as in 2013 when she “smelled” Herfel’s cancer. Sierra was right again—the cancer had returned—but this time in Herfel’s liver. Sierra also confirmed a third recurrence of cancer in 2016.
Sadly, Herfel passed away on July 8, 2021, at 54, after an eight-year battle with ovarian cancer and acute myeloid leukemia. However, had it not been for Sierra’s keen sense of smell, Herfel may not have had the additional eight years with her family.
9 Heidi the German Shepherd-Lab Mix
Anne Wills’s dog Heidi, a German shepherd-lab mix, worked as a search and rescue dog. While Heidi had saved thousands of lives, Wills could never have imagined that Heidi would also save her life.
In February 2015, Heidi began exhibiting strange behaviors each time Wills would sit down—refusing to let Wills up, scratching her arm, and panting excessively, almost as if in a panic. From there, Heidi began pressing her nose into Wills’s chest, taking deep breaths.
Assuming something was wrong with her canine companion, Wills took Heidi to the vet. However, after Heidi received a clean bill of health, Wills realized that Heidi might, in fact, be sensing something was wrong with her instead.
Wills made an appointment to see her doctor, and after being sent for a CAT scan, she was informed that she had lung cancer. She underwent surgery along with intensive chemotherapy and radiation treatments with Heidi by her side every step of the way. Sadly, Heidi passed away from cancer on December 24, 2015.
8 Victoria the Treeing Walker Coonhound
Lauren Gauthier of Buffalo, New York, is the founder of Magic’s Mission Beagle and Hound Rescue, an animal rescue organization that saves dogs from abusive and neglectful situations.
In 2017, Gauthier took in Victoria, a treeing walker coonhound with an infected eye, who had been surrendered by a hunter. Gauthier never realized that not only was she saving Victoria but that Victoria would also save her.
In the spring of 2017, Victoria began staring at Gauthier’s face and putting her nose directly on an area that Gauthier had assumed was simply a pimple or blemish. Victoria would repeatedly touch Gauthier’s nose, look at her, and then smell the area again. When Victoria’s behavior persisted, Gauthier decided to see a doctor.
Gauthier had a biopsy, revealing that the “dot” on her face was actually a basal cell carcinoma. However, thanks to Victoria’s heightened senses and persistence with her owner, Gauthier was able to catch the skin cancer in the early stages and undergo surgery to have it removed.
7 Troy the Doberman Pinscher
Diane Papazian and her husband Harry already owned a fox terrier. However, in 2011, Harry insisted they add Troy, a four-month-old Doberman pinscher, to their family. Given Papazian’s allergies, she was a bit hesitant, but she and her husband ended up bringing Troy into the family… a month earlier than expected. What Papazian did not yet understand was that Troy was meant to come into her life at the time he did.
As the tiny pup was lying in bed with the couple, Troy continued to nuzzle against Papazian’s left side, which caused an allergic reaction to her skin. As Papazian began scratching, she noticed a lump in her left breast.
Papazian had undergone a routine mammogram six months prior, and the results were normal, but after feeling the mass, she got in touch with her doctor. That lump turned out to be stage 2 breast cancer. Papazian had a double mastectomy, started chemotherapy treatments, and was later deemed cancer free, all thanks to their new pup.
6 Daisy-May the West Highland Terrier
In April 2017, 68-year-old Thelly Price’s west highland terrier, Daisy-May, began constantly sniffing around Price’s neck and throat. At first, Price couldn’t see or feel anything that would contribute to Daisy-May’s strange behavior. However, Daisy-May’s nose was spot on.
On May 17, 2017, Price went to the doctor after noticing a lump in the exact area that Daisy-May had been sniffing. Her doctor assumed she had a fatty lump, but after being referred to an ear, nose, and throat clinic for further evaluation, Price was diagnosed with non-Hodgkin’s lymphoma.
Thankfully, due to Daisy-May’s keen sense of smell and early detection, Price was able to undergo surgery without the need for radiation or chemotherapy.
5 Kransky the Miniature Dachsund
As Claire Seeber was curled up on the couch talking to her mother shortly after the Christmas of 2019, her “mini-sausage dog,” Kransky, began incessantly sniffing a mole on her right calf. While Seeber laughed at the tickling sensation, what Kransky discovered was no laughing matter.
Seeber explained her laughter to her mother and what was going on during their call. Given Kransky’s behavior, her mother urged her to get checked out. However, Seeber brushed off Kransky’s actions and her mother’s advice as simple paranoia. Nevertheless, Seeber’s mother wouldn’t back down, so she finally gave in and made an appointment.
As soon as her doctor took one look at the mole, he insisted that it needed to be removed and sent for biopsy. A few days later, Seeber’s doctor confirmed that she had a cancerous melanoma.
Seeber was scheduled for surgery to remove the surrounding cells and ensure that all of the cancer was gone. Thankfully, the surgery was a success which meant Seeber would not need any radiation or chemotherapy treatments, and best of all, Kransky was by her side the entire time.
4 Lola the Chihuahua
Approximately 10 days before Christmas 2020, 41-year-old Tess Robison’s chihuahua, Lola, began acting incredibly strange—smelling Tess’s breath, staring at her, and acting more needy than usual. Then, in a desperate attempt to get Robison’s attention, Lola jumped on her stomach. Two days later, a lump appeared.
Robison immediately made an appointment with her doctor, but it was uncertain what the mass was. Robison was then referred to several different hospitals before being diagnosed with stage 3 low-grade serous carcinoma, a rare form of ovarian cancer, in January 2021.
In March 2021, Robison underwent a 12-hour surgery in which a full hysterectomy was done. However, during the operation, doctors also discovered that cancer had spread to Robison’s bowels. Between the surgery and regular chemotherapy treatments, Robinson is now on the road to recovery.
3 Broady the Newfoundland
Forty-five-year-old Lucy Gies of Didcot, Oxfordshire, adopted Broady, a 154-pound (11-stone) Newfoundland in July of 2021 when his previous family was no longer able to care for him. Unbeknownst to Giles, the “gentle giant” would be more of a blessing than she would ever realize.
By September 2021, Broady began acting strange, and each time Giles would sit down, he would sniff and nuzzle her right armpit. Initially, Giles assumed Broady simply wanted extra attention. However, one morning as Giles was taking a shower, she decided to do a breast exam. That’s when she felt a lump in her right armpit.
Giles’s doctor believed that the lump was hormone related, but when weeks passed with no change, Giles was sent to the hospital for testing. Giles was diagnosed with HER-2 positive breast cancer and was told she also had cancer cells in her lymph nodes.
In October 2021, Giles began six rounds of chemotherapy, then had a lumpectomy followed by radiation treatment. Giles is currently still going through chemotherapy.
2 Bessie the Cairn Terrier
Ron Wain and his partner of Newhall, Yorkshire, rescued their Cairn terrier, Bessie, when she was only 10 months old. However, in 2018, after spending 12 years with the couple, Bessie exhibited behavior that was out of character, such as constantly watching Wain’s every move, following him around, and laying on his chest.
Around the same time Bessie began behaving strangely, Wain noticed he was having to make more trips to the restroom than normal. In light of Bessie’s odd behavior and his increased restroom visits, Wain decided to bring the issue to his doctor’s attention. Wain was then diagnosed with bladder cancer.
Unfortunately, Wain’s first operation was unsuccessful in removing all the cancer, so he opted for a bacterial treatment, which uses a strain of tuberculosis called bacillus Calmette-Guerin (BCG) to treat non-invasive bladder cancers. Once Wain was at the end of his treatment, he was told his cancer had cleared. Bessie, too, stopped following Wain around and went back to her normal behavior.
1 Buster the Jack Russell Terrier
In the spring of 2014, Mike Wagner of Deering, New Hampshire, was lying in bed without a shirt when his dog Buster, a Jack Russell terrier, laid his head on Wagner’s chest and began nudging him. It was then that Wagner noticed a lump on his chest.
Wagner didn’t think too much of the lump and continued his work as a logger for the next few months. However, he began to notice that while he was working and pulling wood, every time he moved his arm, he got an odd feeling in his chest.
Wagner then made an appointment to get checked out. He was referred to a breast cancer center where a biopsy was done, and he was diagnosed with breast cancer. Wagner underwent surgery to remove the cancer, but during the procedure, the doctor realized it had also spread into Wagner’s lymph nodes.
In an attempt to rid his body of cancer, Wagner then went through five months of chemotherapy and six months of radiation. He officially had his last treatment on October 2, 2015.