THE SCIENCE

Why Mosquitoes Bite Your Ankles

— and how volatiles stop them

You’ve probably noticed it. You’re standing at a summer barbecue, arms and shoulders completely fine, while something is quietly making a meal of your ankles. It isn’t random. There’s a precise biological reason — and understanding it is exactly why plant-derived volatiles work so well.

Step one: the CO₂ trail

Every breath you exhale sends a plume of carbon dioxide drifting into the air around you. For a female mosquito, that plume is a navigation beacon. Research has confirmed that mosquitoes can detect CO₂ from up to 50 metres away, using it to orient themselves and fly upstream toward a host. CO₂ doesn’t just attract them — it primes their entire sensory system, sharpening their response to heat, body odour, and movement at the same time.

Why your ankles, specifically?

Here’s where the physics comes in. CO₂ is heavier than the surrounding air. In still or low-wind conditions, exhaled CO₂ sinks toward the ground, pooling at floor level rather than dispersing evenly. A resting or standing person creates a column of gas that settles around their feet — and that’s the zone the mosquito follows.

Once close, the mosquito shifts from CO₂ tracking to short-range cues: skin bacteria on feet and ankles produce distinctive volatile organic compounds (VOCs), feet are warmer and more humid due to footwear, and ankles are exposed but harder to defend against a swat. Research from the University of California, Riverside found that the very receptors mosquitoes use to detect CO₂ are the same ones that detect skin odours — which explains why worn socks and bedding are such effective mosquito lures even without a body present.

What plant volatiles actually do

This is where the science gets genuinely interesting. Essential oils are complex mixtures of volatile organic compounds — terpenes, alcohols, esters, ketones — that plants produce as their own chemical defences. When applied to skin, these same compounds interfere with the mosquito’s olfactory system in several documented ways:

Masking.  Aromatic esters released from volatile compounds can chemically mask the CO₂ and skin-odour signals the mosquito is trying to detect. The pleasant-smelling compounds essentially impersonate a non-host, or simply crowd out the chemical signals that say “warm-blooded creature here.”

Receptor interference.  Mosquitoes detect odours through odorant receptors (ORs) that form ion channels in their sensory neurons. Research has confirmed that specific plant-derived compounds act as allosteric antagonists — they bind to the receptor’s co-receptor subunit (ORco) and block it from functioning, effectively switching off the mosquito’s ability to process scent signals. The result is a kind of chemical anosmia: the insect loses the ability to locate a host.

Confusion and disorientation.  Some volatile compounds over-stimulate CO₂ receptor neurons — flooding them with signals until they can no longer distinguish a real host cue from background noise. Studies have shown that prolonged activation of CO₂-sensing neurons causes mosquitoes to lose directional orientation entirely, disrupting the precise zigzag flight path they use to track a plume.

Competing sensory signals.  The increase in aromatic compounds in the local environment can also excite competing behavioural responses — essentially giving the mosquito conflicting instructions that interrupt host-seeking altogether.

Spray vs. balm — different jobs, same science

Both formats work through the same volatile mechanisms above, but they serve different needs and behave differently on the body.

THE SPRAY	THE BALM
Rapid volatile release	Sustained slow release
A spray distributes a fine layer across a larger surface area quickly. The volatiles begin evaporating almost immediately, creating a scent barrier around the skin. Coverage is broader and application is fast — ideal for arms, legs, and exposed areas before heading outdoors. Because the carrier evaporates, the volatiles are the primary active layer.	A balm format binds the volatile compounds into a wax or oil base, which slows evaporation significantly. Rather than releasing all at once, volatiles diffuse gradually from the base over a longer period. This makes the balm particularly suited to the ankle and foot zone — exactly where CO₂ pools — providing a longer-lasting, localised barrier precisely where bites are most likely.

Think of the spray as your broad perimeter and the balm as targeted ground-level defence — addressing the CO₂ pooling phenomenon directly at the site most mosquitoes are navigating toward.

Why Australian botanicals?

Australia’s unique flora has evolved under significant insect pressure over millions of years, producing some of the most chemically complex essential oils found anywhere. The continent’s botanical diversity means local species have developed volatile profiles that are both potent and genuinely distinct from their northern hemisphere counterparts. That complexity translates directly to the multi-mechanism action described above: more compounds means more simultaneous pathways of interference.

The science supporting plant volatiles as mosquito repellents has grown substantially in recent years, moving well beyond folklore into peer-reviewed biochemistry. What’s been understood intuitively for generations — that certain plants keep insects away — now has a detailed molecular explanation. And it turns out the humble ankle was always going to be the front line.