Dogs’ Sense of Smell
Dogs have an incredibly powerful sense of smell that is far superior to humans. Dogs have up to 300 million olfactory receptors in their noses, while humans only have about 6 million (1). This means dogs can smell odors that are up to 100,000 times weaker than what humans can detect (2). Dogs have been shown to detect some odors at concentrations of only a few parts per trillion (3). Their powerful noses allow dogs to gather a wealth of information from smells that humans cannot perceive. Dogs use their keen sense of smell to track prey, detect drugs or explosives, find missing people, and even detect cancer in humans.
(1) https://phoenixvetcenter.com/blog/214731-how-powerful-is-a-dogs-nose
(2) https://vcahospitals.com/know-your-pet/how-dogs-use-smell-to-perceive-the-world
(3) https://www.smithsonianmag.com/science-nature/you-actually-smell-better-dog-180963391/
Farts Contain Sulfur
The odor of farts comes from sulfur-containing gases. As digested food moves through the intestines, bacteria help break it down. This process produces gas, which contains sulfur compounds like hydrogen sulfide and methyl mercaptan (Why Farts Smell and What It Means, 2022). These sulfur compounds are what give farts their characteristic rotten egg smell. The sulfur content in gas varies based on the types of food eaten and bacteria present in the digestive tract. Foods high in sulfur, like beans, cruciferous vegetables, dairy, and meat, tend to produce more pungent farts (Why Do My Farts Smell So Bad?, 2023). The human nose is extremely sensitive to these sulfur compounds. It only takes a tiny amount of hydrogen sulfide or methyl mercaptan to make a fart smell foul.
Certain health conditions like digestive infections and metabolic disorders can also increase sulfur gas production, leading to more smelly farts (Why Do My Farts Smell So Bad? Smelly Farts Explained, 2022). While smelling farts may be unpleasant, they are usually not a major health concern. Adjusting the diet to reduce high-sulfur foods and taking over-the-counter treatments for gas and bloating can help reduce fart odor.
Farts Smell Bad to Dogs
To dogs, the smell of farts is extremely potent and unpleasant. A dog’s sense of smell is about 10,000 to 100,000 times more sensitive than a human’s (source). Dogs have up to 300 million olfactory receptors in their noses, compared to only about 6 million in humans (source). This means dogs experience odors on an entirely different level than we do.
The main odor in farts that dogs strongly dislike is hydrogen sulfide, which produces a potent “rotten egg” smell. Even tiny concentrations of this sulfur compound can be detected by dogs (source). So when a human passes gas near a dog, the dog is hit with an intense, unpleasant odor that we can barely smell ourselves.
Dogs also dislike other compounds found in flatus like methanethiol, dimethyl sulfide, and skatole. The overall combination creates an overpowering stench for dogs. It assaults their sensitive nostrils in a way we can’t relate to. So it’s no wonder many dogs want to get away when a human breaks wind near them!
Dogs Dislike Certain Smells
Dogs have a very strong sense of smell, with up to 300 million scent receptors compared to a human’s 5 million (https://www.petdoors.com/blogs/dog/what-smells-do-dogs-hate). This makes them extremely sensitive to odors in their environment. Dogs have likes and dislikes when it comes to smells just like humans do. Certain pungent odors can be unappealing or even offensive to dogs.
Strong smells like citrus, vinegar, garlic, and chili peppers are very unpleasant for dogs (https://happywax.com/blogs/from-the-blog/what-scents-do-dogs-hate). Their strong nose leads them to avoid these types of smells whenever possible. The sulfur compounds in farts produce a very potent odor that dogs find repulsive. Pungent odors can overwhelm their sensitive sense of smell, which is why dogs will often leave the room or area when someone passes gas.
Farts Signal Rude Behavior
Dogs have a strong sense of etiquette regarding bodily functions. They typically avoid passing gas around others if they can help it. Studies show that dogs view farting as an impolite bodily function. They do not understand that farting is normal human behavior and may view it as an offensive gesture instead.
To a dog, deliberately farting in their face is extremely rude. They have no way to escape or avoid the unpleasant odor. Dogs abide by a social code of not passing gas in close proximity to others if possible. When a human farts right in a dog’s face, it violates their sense of polite bodily etiquette. The dog has no choice but to sit there and take it.
Dogs rely on bodily signals, routines, and rituals to understand social order. Farting in a dog’s face subverts their expectations. They have no frame of reference to understand why a trusted human companion would show such a vulgar display right in their face. To a dog, this can signal that their human is being aggressive or impolite. Rather than retaliate, dogs may cower, flee, or act anxious when presented with such a rude gesture.
Dogs Can’t Escape the Smell
Dogs have a remarkably strong sense of smell that is 10,000 to 100,000 times more acute than humans 1. Their superior olfactory abilities allow them to detect odors at incredibly low concentrations. Unfortunately for dogs, this means they often can’t escape or ignore strong smells, like the hydrogen sulfide in human flatulence, even if they want to.
Since dogs live in close quarters with humans, they are frequently subjected to the odors we produce. A dog resting by your feet or sitting beside you on the couch is forced to inhale when you pass gas nearby. While the fart may quickly dissipate or go unnoticed by humans, a dog’s sensitive nose has no choice but to process the unpleasant odor.
A dog’s superior sense of smell means they have a difficult time ignoring or escaping from the smell of human flatulence, even though they may want to get away from the unpleasant odor.
Farts Can Signal Aggression
In nature, fart-like odors can represent territorial threats. For example, skunks release a noxious spray when feeling threatened as a defensive mechanism. So when a dog smells a similar foul odor like a human fart, it can put them on alert
Dogs have very sensitive noses, with up to 300 million scent receptors compared to a human’s 5 million. So smells that seem minor or go unnoticed to humans can be very pronounced for dogs (Source). Since passing gas produces a strong sulfurous odor, it can register to a dog as a potential threat or territorial display from another animal. This may explain why some dogs seem apprehensive or even scared when they hear or smell a human fart.
Dogs Don’t Understand Farts
Dogs don’t have the same biological urges to pass gas like humans do. Since dogs don’t fart in the same way, they don’t understand why humans pass gas. According to Rover’s dog health blog, “Dogs don’t actually fart as often as humans do.”[1] Unlike humans who fart for physical reasons, dogs pass gas when they ingest foods that cause gas or eat too quickly and swallow air.
Because farting isn’t a common part of being a dog, they don’t comprehend the process. When a human farts, dogs may be startled, confused, or even upset. They don’t know why their owner is making strange noises and smells. Since dogs primarily communicate through body language and scent, human farts are perplexing to dogs. They don’t speak our language of passing gas.
[1] “Why Do Dogs Fart So Much (and How You Can Help).” Rover, https://www.rover.com/blog/why-do-dogs-fart/
Dogs Dislike Loud Sounds
Dogs have very sensitive hearing and loud sounds can easily startle or frighten them. Dogs can hear at higher frequencies and volumes than humans, so noises that may not bother us can be painful and jarring to a dog’s ears (Source: https://www.akc.org/expert-advice/training/coping-with-loud-noises/). Sudden loud noises like fireworks, gunshots, or thunder are common causes of noise phobia in dogs.
The loud sound of a fart can also startle a dog, due to their sensitive hearing. The abrupt and unexpected sound is alarming to dogs, and they have no idea where the sound is coming from or why it happened. Loud farts that make an explosive sound can be particularly jolting and upsetting for a dog. Since dogs don’t understand the context or reason for the loud fart noise, it understandably scares and confuses them.
Dogs may react to a loud fart noise by cowering, hiding, shaking, or showing other signs of fear. Some dogs may even become aggressive toward the source of the sound. Loud farts can be unavoidable accidents, but it’s best to try to minimize exposing dogs to abrupt loud noises that can damage their hearing or make them fearful.
Dogs Read Body Language
Dogs rely heavily on body language signals from their owners to understand situations and guide their behavior. According to this article, dogs recognize human facial expressions like smiling and frowning. Dogs can also detect subtle shifts in body posture and movement that give insight into a person’s emotional state.
When an owner loudly or forcefully farts near their dog, this can signal unwanted behavior in the dog’s eyes. The abrupt body movement and rude noise contrasts with most human-dog interactions and may put the dog on edge. Dogs aim to please their owners and look for positive feedback. Aggressive farting goes against this and can confuse dogs who rely on body language cues to gauge proper responses.