Homeopathic "medicine" is nothing but a placebo. It appears to work only because the act of taking the remedy psychologically influences the patient to feel better. Or they just get better on their own and attribute the healing to the homeopathic remedy.
Homeopathic remedies can not have a physical effect on the patient due to the way they are prepared. One of the basic principles of homeopathy is that substances become more potent the more they are diluted. Homeopathic dilution, or "potentization" is measured by the C scale - 1C is a dilution of one part substance to 100 parts water. 2C is a second dilution of the 1C solution by 100 parts water, making it a concentration of 1/10,000. Over-the-counter homeopathic remedies are sometimes sold at 6C dilutions - a one part per trillion concentration of the original substance, but are considered most effective at 30C or more - even up to 200C.
At any dilution greater than 12C, it is nearly impossible that any molecules of the mother tincture are left, and unlikely that any of the water molecules even came into contact with it. At 200C, you'd need a glass of water the size of the observable universe in order to ensure that you were drinking just one molecule of the substance.
Since homeopathic remedies cannot possibly work chemically, homeopathsa claim that the water somehow "remembers" the mother tincture, even though there are no molecules left. How the water remembers that it once touched a drop of milk thistle but forgets all the times it has been cat urine is a convenient mystery.
You can read more in my hub on this topic: