repellent

Anything whose smell, taste, or other properties discourages nearby creatures. Insect repellent is usually a chemical substance that keeps, for example, mosquitoes at bay; natural substances include citronella, lavender oil, and eucalyptus oils. A device that emits ultrasound waves is also claimed to repel insects and small mammals.

The bitter-tasting denatonium saccharide may be added to medicines to prevent consumption by children, and to plastic garbage bags to repel foraging animals.