The iodine phenomenon is one of the methods for diagnosing various diseases, which is based on the body’s response to the introduction of iodine. This method was developed in 1947 by the Swedish scientist Jadasson and has since been widely used in medicine to diagnose various diseases. The essence of the method is that when iodine is introduced into the body, a reaction occurs between iodine and skin proteins, which manifests itself in the form of redness of the skin and the formation of an iodine network. This reaction can be used to diagnose many diseases, such as tuberculosis, syphilis, malaria, cancer and others. To conduct an iodine test, a small skin incision is made on the patient's skin, after which iodine is injected into the wound. After a few minutes, the skin begins to turn red, and then a network of red stripes forms on it. If an iodine network forms on the skin, this means that the patient's body is reacting to iodine, and this may indicate the presence of a disease. The iodine phenomenon can also be used to diagnose thyroid diseases. When iodine is introduced into the body, a reaction occurs between the iodine and the gland, which can be used to determine the level of thyroid hormones in the blood. In general, the iodine phenomenon is one of the most accurate methods for diagnosing various diseases and can be used in various fields of medicine.