Homeopathy started about 200 years ago with a discovery by the German doctor Samuel Hahnemann. Homeopathy means literally to "treat with a similar disease" and this principle is often made more clear by contrasting it with other methods of treatment. For example, "allopathic or conventional treatment" uses methods based on counteracting a symptom such as using a drug to slow intestinal motility in a case of diarrhea.
To understand the homeopathic approach, it is helpful to consider the state of the patient during disease. There is the immediate cause such as a bacteria, virus, toxin, or internal, immunological activity. There is also the patient's side of the problem with the manifestation of reaction and defenses (e.g. fever, inflammation and discharge - attempts at eliminating the source of the problem).
The homeopathic perspective does not ignore the existence of immediate causes such as infection, but focuses more on the how the patient is attempting to deal with the problem. The idea is that if the patient's defenses can be strengthened to fight the disease, then the balance shifts in favor of recovery.
The central discovery that Dr. Hahnemann made is that the patient can be stimulated towards recovery when medicines are applied in a particular way. If the patient is given a substance that will gently disturb the health in the direction of "disease" to produce almost the same syndrome or the same set or symptoms (in mild form), it will have a stimulating effect on the patient's defense system. It is almost as if the patient's defenses cannot distinguish between the natural disease and what this similar substance is doing.
The usefulness of this method is that medicines can be used to manipulate the patient's condition; to enhance and assist the attempts that the patient is making to overcome the disease.
The homeopathic approach utilizes several hundred substances that have been studied as to their effects on the human and animal body. Some of these are common herbs; others are from poisonous plants; some remedies are made from toxins and venoms.
To enhance the usefulness of these substances while minimizing harmful effects, homeopathic medicines are specially prepared in pharmacies. They are carefully diluted and mixed to a level where stimulation is still possible but toxic effects are eliminated. This is somewhat similar to the method of desensitization against allergens or the use of vaccines. In summary, the method of homeopathic treatment is to stimulate the process of healing through temporarily establishing an artificial disturbance of health with medicines. This disturbance, when similar to the disturbance caused by the disease, makes the body work harder at trying to get well. The healing changes that follow are the result of this stimulation.
The homeopathic doctor carefully evaluates the changes that occur after use of the homeopathic medicine. In this way, patients can be guided to recovery of their health over the weeks or months necessary for the body to repel the disease and regrow damaged tissues.