Eating onions, broccoli, Brussels sprouts or other cruciferous vegetables can lead to the skin smelling like onions. Compounds in these vegetables are broken down in the digestive tract, enter the circulatory system and are excreted via the mouth, lungs and skin.
Some bacterial infections of the vagina can also smell like onions. Diabetes, liver disease, infections and hyperthyroidism can all cause persistent body odors. Uncontrolled diabetes often causes a fruity-smelling body odor. Individuals with liver or kidney disease can smell odd in a way that is described as similar to the odor of bleach. Changes in body odor that do not seem to be linked to temporary dietary choices should be investigated by a doctor.