“It’s both sticky and slippery,” David Hu says of the brownish substance inside the ear canal. New research published in the journal Soft Matter shows that human earwax combines these unexpected properties to function as a physical defense mechanism that deters small insects like ants.
Experimental Findings on Ants and Earwax
Researchers analyzed the mechanical and chemical properties of 36 earwax samples from humans, dogs, cows, sheep, pigs, and rabbits, and observed how fire ants reacted to natural and synthetic earwax. While ants easily scale kitchen cabinets, they flounder on earwax. Hu explains that earwax sucks moisture from the ants’ feet to disrupt their grip, while the substance simultaneously sticks to their bodies, causing the insects to groom incessantly. When placed on a thin layer of earwax coating a glass slide or beaker rim, ants slip right off. The chemical makeup consists of 60 percent dead skin cells, along with oils, moisture, and ink bottle-shaped pores that allow it to absorb twice its weight in water.
Earwax Could Inspire Nontoxic Pest Control Surfaces
“[This] familiar biological material may represent a sophisticated physical defense against small arthropods,
” says Stanislav Gorb, a functional morphologist at the University of Kiel in Germany, who was not involved with the work. Gorb suggests that earwax “could inspire a new generation of physical, nontoxic pest control surfaces,” which might provide coatings to protect stored food, agricultural products, and technology. Meanwhile, Hu notes that turning earwax into a commercial insect repellent is impractical because each person has only a volume of earwax equivalent to a grain of rice in each ear at any given time.
