The theory behind homeopathic medicine is that “like cures likes,” and that a substance that causes an illness in a healthy person might cure those symptoms in someone who is ill.

It’s believe by practitioners of homeopathy that a small amount of the substance which causes a disease will stimulate the body to heal itself.

Though this may sound far-fetched, the theory is somewhat analogous to the basis of vaccination in modern-day medicine: with immunizations, the exposure to a small amount of a killed or inactivated microbe can result in protection against developing the disease.