Can People Smell Ants? The Weird Little Science Story Behind A Real Sensory Difference

If you have ever told someone you can smell ants and been met with confused silence, you are not alone. The ability to detect the smell of certain ant species is real, well-documented, and unevenly distributed in the human population. Here is the short scientific explanation of what is going on.

What ants smell of

Many ants release a chemical called formic acid when they are alarmed or crushed. The most-cited example is the European wood ant (Formica rufa), which can spray formic acid as a defence and gives off a sharp, vinegary, slightly citrussy smell that is often compared to bleach mixed with vinegar.

Other ant species use different defensive chemicals. North American odorous house ants (Tapinoma sessile) release a methyl-ketone compound that gives them their common nickname: when crushed they smell, depending on the nose, of rancid butter, pine, or, most often reported, blue cheese.

Why some people can smell them and others can't

Human olfactory perception varies enormously. Around 400 functional olfactory-receptor genes are spread across the human genome, and individuals carry different combinations of working and non-working versions. The ability to detect any specific aromatic compound, formic acid, the methyl-ketone in odorous house ants, or many others, depends on whether the receptors that respond to that compound are functional in your nose.

This is the same reason some people experience asparagus urine, why coriander tastes like soap to a minority of people, and why the same hallway can smell strongly of damp to one family member and of nothing at all to another.

Is it always the ant?

Not necessarily. People who report being able to "smell ants" sometimes are picking up the formic acid plume from a colony, but they may also be smelling crushed ants, ant pheromone trails along skirting boards, or even chemical residues left after a colony has been disturbed. In a kitchen with a colony in the wall cavity, the smell can persist long after the visible ants have gone.

The takeaway

Yes, some people can smell ants. The smell is real, the chemistry is well-understood, and the variation between individuals is mostly genetic. If you are the person in your household who notices the smell, you are essentially the early-warning system. Take it as a small evolutionary compliment.