Naturopathic doctors combine these understandings about health and disease, knowledge of physiology and biochemistry, and modern diagnostic tools including physical exam, lab tests and imaging, to identify the sources of disease. Through nutritional, botanical and homeopathic medicines, naturopathic medicine can help re-establish health by stimulating the immune system and detoxification pathways, by directly fighting infections, or by promoting specific hormone or neurotransmitter synthesis. The traditional medicines used in naturopathy often have long histories of use that provide us with information about safety and efficacy. Many of the most commonly used herbs and nutrients have more recently been the subjects of scientific research attempting to better understand their biological activities and medicinal properties, in many cases verifying what was known historically. Naturopathic interventions can be used effectively for chronic conditions and for non-life-threatening acute ailments such as colds and flus. Annual physical exams and screening lab tests can also be performed by naturopathic doctors.