Lye is an end product of salt extraction in which sea water, after staying in evaporators and salt-pans and crystallization, remains above the salt layer as a thick oily odourless opaque liquid. It contains all elements and micro elements of sea water – potassium, sodium, calcium, magnesium, iron, copper, zinc, strontium, etc. The effect is multiple with thermal, chemical and mechanical factors. The thermal factor is especially important for the medicinal results – lye has a high heat-absorbing capacity and low heat conductivity, making it a good physiological activator. The chemical effect is caused by the passage of ions, water-soluble substances, salts and micro elements through the skin. Mechanical treatment speeds up the lymphatic and venous flow. The effects on the body after the procedure are: improved blood supply, faster resorption and dispersion of pathological products, reduced bloating and pain, improved metabolism and faster healing processes.