The invention provides a method for enhancing immunosurveillance capacity, particularly, NK cell activity, without administration of medicines or immunological therapy, through a noninvasive and simple method. The invention also provides a method for enhancing power of concentration of users in intellectual activities. The method according to the invention is carried out by applying to the forehead, with foreign lights being excluded, a pulsed light in the frequency range of from 0.5 to 13 Hz, preferably in a frequency of a representative value in alpha wave band obtained by measuring brain waves of users or any frequencies near that representative value. NK cell activity is surely enhanced by the pulsed-light application with the eyes of users being shielded.
Method of noninvasively enhancing immunosurveillance capacity