The method involves evaporating of treatment liquid under formation of vapor stream, and cooling the vapor stream by supplying a gas, particularly ambient air in the vapor stream. The gas is present at ambient temperature and is cooled against temperature of the steam. A low temperature vapor stream is initiated in a treatment vessel (13) which is formed for inserting or applying a body part to be treated with the low-temperature steam. The low temperature vapor stream is provided by cooling. An independent claim is also included for a vaporizer for applying steam to a human body part.
