Onions have been useful for treating various human diseases such as tumors, persistent coughs and cold. Medicine practitioners consider this plant form as a perfect home remedy for relieving disease syndromes. Onion consumption can help in prevention of stomach and breast cancer. Onions are often used to prevent tooth decay and oral infections. Onion Oil aids in thinning of the blood, which in turn prevents the red blood cells from forming clumps. These blocks could lead to heart disorders or cardiovascular diseases.