We all think we know dogs. They’ve been our companions for thousands of years, and yet some surprisingly stubborn myths about them still linger. It doesn’t sound like a problem, but these myths can have real effects on the way we care for our pets. From how quickly they age to their visual capabilities, the gap between popular belief and scientific fact is wider than most people realise.
Here are five of the most common dog myths, supported by scientific evidence. It doesn’t matter if you’re a first-time dog owner or a lifelong pet lover, you might learn some important truths.
Myth 1: One dog year equals seven human years
This is perhaps the most well-known dog “fact” and one of the most misleading. The 7:1 ratio seems to have originated from a simple mathematical comparison, that humans live to roughly 70 and dogs to roughly 10.
But dogs don’t age at a steady, predictable rate. According to the American Kennel Club a more accurate guideline looks like this:
- The first year of a medium-sized dog’s life equals approximately 15 human years
- The second year adds around 9 more human years
- After that, each dog year is roughly equivalent to 5 human years
That means a two-year-old dog is closer to a 24-year-old human, not a 14-year-old as the traditional rule would suggest.
Size also plays a significant role, with smaller breeds often living much longer than bigger breeds.
Myth 2: Humans can catch fleas from dogs
They can, but not in the way most people think.
Fleas can bite humans, but they cannot survive on us as permanent hosts. Dog fleas aren’t able to live on humans because they need dog blood to survive, and humans don’t provide enough warmth or hair coverage to be a viable long-term home.
So, whilst you might notice an itchy bite around your ankles (which often appear in small clusters on the legs), fleas are unlikely to take up permanent residence on your body.
That said, if your dog has fleas, your home is probably infested too. Fleas progress through four lifecycle stages: egg, larvae, pupae, and adult. Adult female fleas can lay up to 50 eggs per day, and those eggs can fall off your pet into carpets, bedding, and furniture. This is why treating just your pet alone isn’t enough, you must view this comprehensively and treat your home too.
Effective flea prevention requires a two-pronged approach:
Treating your pet: Products like Johnson’s Guardian Plus Spot-On help to protect your pets by killing adult fleas and preventing the development of eggs and larvae. You can also use our 4Fleas tablets which starts killing fleas within 15 minutes, alongside spot on treatments.
Treating your home: Vacuum thoroughly and regularly, wash all bedding and soft furnishings at 60°C or above. Then apply a household flea spray such as Guardian Home Flea Spray, which can provide up to six months of protection.
Skipping the home treatment is one of the most common reasons flea infestations keep coming back. Even after your pet appears flea-free, dormant pupae can remain in carpets and crevices for weeks or even months before hatching!
Myth 3: Dogs can see perfectly in the dark
Dogs are often credited with impressive night vision. The truth is, whilst dogs do see better than humans in low light, they still rely on some light to see.
Their advantage comes down to three key anatomical features;
- Tapetum lucidum: A reflective layer of tissue behind the retina that acts like a mirror, bouncing light back through the retina a second time so dogs can make better use of available light. This is what causes that distinctive eye glow in photographs.
- Rod-dominated retinas: Dogs have far more rod cells than humans. Rods are the photoreceptors responsible for detecting motion and shapes in dim conditions, which gives dogs a significant advantage at dusk or in low-light environments.
- Larger pupils: Dogs’ pupils can dilate much wider than ours, allowing more light to enter the eye.
Interestingly, dogs have better night vision than humans but somewhat inferior night vision to cats, whose tapetum lucidum reflects even more light and vertical-slit pupils allow for greater light intake.
Myth 4: Dogs are colour blind
Dogs are not completely colour blind. They do, however, see a more limited colour range than humans. A dog’s colour vision is dichromatic, meaning they perceive the world through two colour channels rather than three.
Humans have three types of cone cells in their eyes, allowing us to distinguish red, blue, and green. Dogs have just two types, making their colour perception most similar to a person with red-green colour blindness. Dogs see blues and yellows well, but reds and greens appear as shades of brown or grey.
In practical terms, that bright red ball you throw in the green grass for your dog to chase likely blends right in. A yellow or blue toy would be far easier for them to spot.
This is also one reason the popular children’s animated series Bluey uses a predominantly blue and yellow colour palette, which creators say they chose while working with scientists to create a show that appealed to both humans and dogs.
Myth 5: Leaving a dog in a hot car for a short time is safe
This is the one myth with the most serious consequences, and it needs to be stated clearly: there is no safe amount of time to leave a dog in a hot car.
Dogs are unable to regulate their body temperature the way humans can. We sweat all over our bodies, whereas dogs primarily pant. In an enclosed vehicle, this quickly becomes insufficient.
The RSPCA states that when the outside temperature is just 22°C, the interior of a parked car can reach 47°C within an hour. Even with windows slightly open, temperatures rise at a dangerous rate. The shade offers very little protection, as ambient heat builds rapidly regardless.
Heatstroke in dogs can develop within minutes. Signs include excessive panting, drooling, glazed eyes, vomiting, and collapsing. If you see a dog in a car alone on a hot day, call 999 immediately and follow instructions given by the call handler on what to do next.
Better knowledge means better care
These myths aren’t harmless. They shape decisions from how we protect our dogs against parasites, to how we assess their health, to life-or-death choices about leaving them unattended in vehicles.
The science behind them is clear and applying it is straightforward. Addressing these myths is another way of encouraging and promoting responsible pet ownership. When in doubt, consult your vet. They’re the best source of evidence-based guidance tailored specifically to your dog’s breed, age, and lifestyle.
