Medicinal plants and mushrooms affect many physiological functions of our body through the content of biologically active components. These agents, so called immunostimulants, either interact with the immune system stimulating the production of specific chemical compounds or enhance the phagocytic activity. In the contrary, they can also possess immunosuppressive effects. To increase immune functions in our organism people all around the world traditionally use herbal teas or other food supplements and their efficacy can differ based on their composition. This study summarizes fundamental principles of human immune system, reviews the knowledge on the most studied and farmacologically used medicinal herbs and mushrooms and describes the possibility of modulating the immune system by food. Herbal and mushrooms infusions were tested for their potential activity to stimulate phagocytosis of granulocytes. These were isolated from buffy coats and tested on phagocytic activity on opsonized zymosan particles in 96-well plates. The activity was monitored using the luminiscence rader and was evaluated in terms of phagocytic index and minimal stimulating (MSC) and minimal inhibiting (MIC) concentrations. Out of 25 extracts tested, immune enhancing activity was observed in 8 extracts, particularly in infusions of Equisetum arvense, Plantago lanceolata, Zingiber officinale, Urtica dioica, Rosa canina and the Lentinula edodes mushroom. The highest immunomodulatory effect was determined in Ganoderma lucidum. Tested tea and mushroom infusions, which were supposed to have immunostimulating effects, proved to be efficient only in one case, Rosa canina tea but both mushroom samples demonstrated high effect on enhancing phagocytosis of granulocytes.