The Chemistry of Dog's Paws

Introduction

Recently a topic has been arising about the oh so familiar smell of our furry friends’ feet. People have been noticing that the smell is similar to that of a Frito or a corn chip. The chemistry of dogs’ paws explains why the pads on a dog’s foot gives off such a smell. The cause lies in the bacteria living in between their toes. More specifically, the byproducts those bacteria produce. I will be going to school to become a veterinarian, therefore I am very interested in everything dogs. After wondering for so long, I decided it was time for an answer. The curiosity is the mainly what will be solved by this project. However, it also teaches about yeast and bacteria, which are all over and around us.

Composition of ...

Proteus Byproducts:

-Hydrogen Sulfide (H₂S)

Yeast Byproducts:

-Dimethyl Sulfide (C₂H₆S) -Ethanol (C₂H₆O)

-Diacetyl (C₄H₆O₂) - Carbon Dioxide (CO₂)

Main Chemicals, Compounds, Components

Dimethyl Sulfide:

-Most abundant biological sulfur compound emitted into the atmosphere, smell of sweet corn

-The MXR7-CA gene in yeast produces C2H6S during brewing yeast metabolism

-Boiling Point: 99.21℉ or 37.34℃ -Density: 840 kg/m3

-Molar Mass: 62.13 g×mol-1 -UN Number: 1164

-Present in healthy people at low levels

Hydrogen Sulfide:

-Colorless gas, poisonous, corrosive, flammable, rotten egg smell

-Product of bacterial (Proteus) decomposition, slow oxidation of various compounds by the air which causes H2S

-Boiling Point: -76℉ or -60℃ -Density: 1.363 g dm-3

-Molar Mass: 34.08 g×mol-1 -UN Number: 1053

-Created by the human body in small doses

Chemistry's Role

Chemistry’s Role in making dogs’ paws smell like fritos is in the byproducts that come from different chemical reactions. There are a couple of prominent naturally occurring bacteria on the bottoms of a dog’s foot and between their toes called Proteus and yeast. The Proteus is naturally occurring just like bacteria in the human body. As the Proteus begins to decompose in the natural cycle of life, the air oxidizes various compounds of proteus. One of them produces Hydrogen Sulfide. The hydrogen sulfide in turn is on the paw and smells like rotten eggs. The yeast is also naturally occurring because it thrives in warm, moist areas such as a dog’s paw. While the yeast metabolizes, a gene called MXR7-CA produces dimethyl sulfide. The dimethyl sulfide then is also on the paw, and it gives off a sweet corn smell. The mixing of the two smells and the perception of the human brain results in a lot of people to believing their four legged friends smell like fritos.

Background Research

The fritos smell emitting from you best friend’s feet is basically caused by chemical reactions in bacteria. The smell is made during the metabolization of yeast, and the decomposition of Proteus bacteria. These take place in between the toes on a dog because it is the perfect warm, moist environment for these organisms to thrive. When yeast metabolizes (breaks down food) a specific gene within it produces Dimethyl Sulfide which in turn smells like rotten eggs. When the proteus decomposes due to the circle of life, the oxidation of certain compounds within the bacteria produces Hydrogen Sulfide which smells like sweet corn. When taking in these two smells at once the human brain perceives it as a similar smell such as fritos or corn chips.

Resources

google.com/amp/s/www.inverse.com/amp/article/30167-dog-feet-paws-smell-corn-chip-fritos

    • Ecrine glands: secrete fluids out through pores in skin, in dogs they only exist on pads of their feet, only sweat through parts without fur
    • Bacteria and yeast: warm, moist environment where microbial communities flourish
    • Depends on what they’re stepping on; mud gives off an earthy scent
    • Chemical composition is complex and always changing
    • Associations and perceptions play a role, the brain only picks out pleasant smells

iflscience.com/plants-and-animals/youre-not-weird-your-dogs-feet-really do smell-like-fritos

    • Bacteria: Pseudomonas and Proteus and yeast
    • Hair growing longer between toes provides the perfect environment to grow, hence the smell

http://blogs.discovermagazine.com/discoblog/2012/07/05/which-bacteria-smell-like-tortillas-flowers-or-delicious-browned-butter/#.WnEswcfWfR0

    • Proteus bacteria are known for their sweet corn tortilla smell

www.beeradvocate.com/beer/101/yeast

    • Yeast has tons of byproducts including but not limited to: dimethyl sulfide (DMS) smell of sweet corn, diacetyl which smells buttery, and ethanol/CO2 which are the main ones

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4638163/

    • Proteus produces hydrogen sulfide which smells like rotten eggs

https://pubchem.ncbi.nlm.nih.gov/compound/2_3-butanedione

    • Composition of Diacetyl

https://en.wikipedia.org/wiki/Dimethyl_sulfide

    • Composition of Dimethyl Sulfide

https://pubchem.ncbi.nlm.nih.gov/compound/ethanol

    • Composition of Ethanol

https://en.wikipedia.org/wiki/dimethyl_sulfide and https://ncbi.nlm.nih.gov/pubmed/12702301

    • Info on Dimethyl Sulfide

About the Author

Elley Munson is a Junior at Billings Senior High. She is involved in soccer, cheer, student council, and senior advocates. Elley plans on attending MSU Bozeman then continuing her education at WSU to become a veterinarian. She enjoys baking, summer, going to her cabin, hiking, and making memories with her friends. And of course hanging out with her dogs.