From chemicals to cheese to animal farts: the world's stinkiest things

Dad farts. Gas station pumps. Skunk spray. Rotten eggs.

There’s few things worse than sitting there and suddenly catching a whiff of a stinky smell. But have you ever wondered what science says is the worst scent out there? 

Well, it’s not such an easy answer – researchers at the Journal of Neuroscience say that although smell comes down to the object’s molecular structure, our brains are also hardwired through evolution to avoid disgusting smells if we want to survive.

They say that typically, heavier, more spread-out molecules tend to seem stinkier, while lighter, more compact molecules are more pleasant. For example, Butanol, an electron-dense and spaced out molecule, smells like rotting wood, while limonene, a compact and light molecule, smells like citrus.

"Part of the olfactory percept is innate and hard wired. For example, laboratory rodents that have never encountered a cat through generations of breeding still react fearfully to cat odour, but not other novel and noxious odours," said the authors of the paper.

But some odours are pretty objectively bad – not only is it in their DNA, but most humans seem to agree. So keep reading if you want to be grossed out by these eye-watering record titles, and just be glad they (most likely) aren’t in your home.

Smelliest substance - US Government Standard Bathroom Malodor

This clear liquid may look unassuming, but it’s made of all the chemicals that make poop smell so bad, combined in their most concentrated form. Humans can detect its presence in concentrations as low as one part malador to 999,999 parts water, which is the equivalent of a teaspoon in an Olympic-sized swimming pool.

Although most people will never find a use for this substance, it did have some military uses. For example, in the 1990s, scientist Pamela Dalton was in charge of making a stink bomb for the Department of Defense, but found that people from different cultures found different scents disgusting. So she used US Government Standard Bathroom Malodor (used to mimic the scent of military field latrines, to test cleaning products) as the base of her “Stench Soup” – which might be the worst smell ever created, described as “Satan sitting on a throne of rotting onions.”

Smelliest cheese - Vieux-Boulogne

Although blue cheese does get a bad rap, it doesn’t hold a candle to the stench of Vieux-Boulogne, the world’s stinkiest cheese (according to science). 

The soft French cow’s cheese is matured for 7-9 weeks and is made by French cheesemaker Philippe Olivier, and in November 2004, scientists at Cranfield University in Bedfordshire, UK, deemed it the smelliest cheese in the world.

Vieux-Boulogne proved smellier than 14 other contenders, when reviewed by a panel of 19 human noses and one electronic – the latter testing for gaseous molecules being released by the sealed cheeses.

The winning cheese was so strong that one journalist described its “farmyard odour replete with dung” as noticeable even at 164 ft (50 m) away. It also beat the notorious Époisses de Bourgogne, a cheese so smelly that it is banned from being taken on public transit in France.

Smelliest flower / plant - Rafflesia arnoldii

The Amorphophallus titanum plant, a bulkier version of the smelliest flower

Although it’s always nice to stop and smell the roses, you definitely shouldn’t stop to smell Rafflesia arnoldii. 

This remarkable record-breaking plant is also known as the largest single flower because of its one mottled orange-brown and white parasitic lump of a flower. But what also turns heads is its smell – it’s also nicknamed “corpse flower” (along with the bulkier Amorphophallus titanum) because of the scent it elicits to attract flies. Its flowers smell like rotting meat!

One specimen discovered in a forest in West Sumatra, Indonesia, in 2020 measured 111 cm (3 ft 7.7 in) across, and they may weigh up to 11 kg (24 lb) with their five fleshy petals reaching up to 1.9 cm (0.75 in) thick. They have no leaves, stem or roots, instead growing as a parasite within jungle vines. Every so often, the buds burst through the vine and grow to their full size, though after months of development, the full-grown flower only lasts for around a week.

And here’s how to recreate the stench of the world’s smelliest plant, if for some reason you want to!

Smelliest bird - the Hoatzin (Opisthocomus hoazin)

While the smelliest mammal is the striped skunk due to its stinking spray (which a human nose can detect if sprayed in the wind a mile (1.6 km) away!), the smelliest bird is a close contender.

The Hoatzin, native to the slow-moving rivers and lakes in the Amazon basin, is a descendant from a now-extinct line of ancient birds, and you can definitely tell – its spiky feathers and blue head looks far off from its closest living relative, the chicken.

But what will definitely turn your head is its smell – the bird eats and digests leaves similarly to a cow, fermenting their food in their gut and producing a manure-like stink. Even its local name, pava hedionda, translates as "stinking pheasant/turkey."

Another fun fact about these birds? They have claws on their wings that allow them to climb!

Smelliest fruit - Durian

The smelliest fruit is much more common to find than a Colombian bird, but you still should heed our warning before buying it as a fun new snack.

Durian, from Southeast Asia, is described as the “king of fruit”. Like an aggressive pomegranate, a thick, thorny armour prevents you from diving into the seeds holding the custardy-looking flesh of the fruit. 

But its pungent smell is what tends to put people off it immediately – in fact, it’s banned to eat this fruit in many hotels and on public transit in Southeast Asia, because it smells like “a combination of sulfur, sewage, fruit, honey, and roasted and rotting onions.”

But for some people's taste buds can pick up on the sweeter components of the fruit’s DNA, and they can enjoy all the health benefits this stinky food has to offer.

Smelliest planet - Uranus

The smelliest planet in the solar system is... Uranus, haha.

No, really. Scientists proved in a study that the planet smells like rotten eggs because of the Hydrogen Sulfide present in the atmosphere – making it one of the smelliest planets to live on (if you were an astronaut).

Uranus also holds the record title for the coldest measured atmospheric temperature on a planet, so it might be best to admire the beauty from afar.

Smelliest frog - Venezuelan skunk frog (Aromobates nocturnus)

If you’re ever walking around Venezuela and catch the overwhelming whiff of skunk, it might be harder to locate than you’d think – because it could be the Venezuelan skunk frog (Aromobates nocturnus).

This tiny creature was unknown to science until 1991, but measuring 6.2 cm (2.44 in) long, it is the largest member of the poison-arrow frog family, Dendrobatidae.

When threatened, the frog has a vile-smelling skin secretion that actually contains the same stink-producing organosulfur compound that is present in the famously foul anal emissions released by skunks.

Smelliest foods - fermented herring and tofu

Contestants eat fermented herring at food eating competition in Sweden

Depending on where you’re from, you might disagree about what foods smell the worst.

But science and culture have raised two dishes to the forefront of the stinky food debate: the Swedish dish surströmming and the Taiwanese dish (aptly-named) stinky tofu.

Both happen to be fermented dishes – surströmming is a type of fermented Baltic herring known for its slimy texture and its disgusting smell like rotten eggs, and stinky tofu is a side dish of fermented tofu whose smell is compared to that of rotting garbage or smelly feet.

Everyone has different taste buds however, and for those who like it fermented, there’s food competitions out there for you if you want to pig out on surströmming or stinky tofu. Just maybe don’t go out on a date after.

And for the record: The most fermented herring eaten in one minute is 392.7 grams (13.85 oz), by Sune Valentin Norlin (Sweden) in Malmö, Sweden, at the Museum of Disgusting Foods in September 2022, and the largest serving of stinky tofu weighed 1,000 kg (2,204 lbs 9 oz) and was made by the Taiwanese government to celebrate Taiwan’s (ROC) 100th anniversary.

Header image: Kenny Eliason / Unsplash