No, there are no side effects of homeopathic medicines. The reason is that the crude medicinal substances like plant, mineral, metal etc. are diluted by a process called potentization to such an extent by which the quantity of substance is reduced and the quality of the substance is at the same time increased. We also know that Disease manifest itself not merely by objective signs (signs observed by those around patient), but also by subjective symptoms (symptoms felt by the patient). Homeopathy is the only medicinal science where data has been collected by proving medicines on healthy human beings, and not on animals; because human beings can communicate their actual feelings during the proving, while animals cannot. Hence homeopathy can be considered as the safest science.