In the European Union and the United Kingdom, onion oil can be used to control carrot fly in umbelliferous crops like carrots, parsnips, parsley, celery, and celeriac. One of the natural oils that is sometimes used in hair oil is also found in onions.

Under low magnification, onions’ particularly large cells are easy to see. The bulb epidermis is simple to separate for educational, experimental, and breeding purposes because it consists of a single layer of cells. Onions are thusly ordinarily utilized in science training to show the utilization of a magnifying lens for noticing cell structure.

Onions are poisonous to canines, felines, guinea pigs, and numerous different creatures.
Boiling onion skins yields an orange-brown dye.

Quercetin, a plant pigment with antioxidant properties in vitro, can be found in onions. According to the findings of a Japanese study, onions aid in the reduction of diabetes-related oxidative stress. According to the findings of another Chinese study, onion juice can help patients with bone conditions like osteoporosis by reducing oxidative stress.