A laser system has a laser source for generating a laser beam, a control unit, and a hand piece for manually guiding the laser beam onto a target area. A wavelength (λ) of the laser beam is in a range from above 1.9 μm to 11.0 μm inclusive. The laser system is adapted for a thermal, non ablative treatment of mucosa tissue by the laser beam such, that the laser source generates the laser beam in single pulses with a pulse duration (tp) in a range from 1.0 μs, inclusive, to 1.0 sec, inclusive, and that a fluence of each of the single pulses on the target area of the mucosa tissue is in a range from 0.2 J/cm2, inclusive, to 2.5 J/cm2, inclusive, and preferably in a range from 1.40 J/cm2, inclusive, to 1.95 J/cm2, inclusive.