Onion contains elements like sulphur compounds and quercetin, in traces of essential oils. Sulphur compounds and quercetin in onion are very effective antioxidants. They help a great deal in neutralizing the free radicals present in our body. For many centuries onion has been used for medicinal usages. Let us see some of the medicinal benefits of onions. Onions are used to avoid tooth decay and oral infections. Onions help in thinning of the blood help prevent formation of blood clumps. Onion juice consumed with honey or olive oil is used for treating acne. Taking equal quantities of onion juice and honey can help in getting relief from sore throat and cough symptoms.