Homoeopathy is a well established form of medicine developed over 200 years ago by Dr. Samuel Hahnemann, who discovered that substances that create disease in large doses, can also cure the same symptoms when diluted. This has become known as the principle of "like cures like".
An example is the remedy Allium cepia (a dilution of the common onion).
When chopping an onion in its raw state the eyes and nose run with a
clear uncomfortable discharge. Once the onion is diluted
homoeopathically making the remedy Allium cepia, it can be used
effectively for those whose eyes and nose run with an uncomfortable
discharge. Like supports like, once diluted.