Onions contain glucose-lowering drugs such as toluene sulfonylurea, prostaglandins, etc., consumption can assist diuretic, vascular protection, but food does not have medicinal properties, can not be used for the treatment and prevention of disease. 1. Diuretic: onions contain the same organic matter as the hypoglycemic drug toluene sulfobutylurea, after consumption of the body’s quercetin has a strong diuretic effect, so consumption can play an auxiliary diuretic effect. 2. Protection of blood vessels: onions contain prostaglandins, can play an auxiliary role in expanding blood vessels, reduce total peripheral resistance, increase coronary flow, while lowering blood pressure, to prevent thrombosis, for hypertension, hyperlipidemia, diabetes patients. Onion can produce volatile gases, easy to stimulate the mucous membrane, is not suitable for gastrointestinal problems and gastrointestinal diseases. Raw onion is easy to cause tears, skin burning sensation and other reactions, itchy skin, eye disease can aggravate the discomfort, consumption should be cautious.