Henna does not harm the eyelashes provided, that it is properly prepared It should be diluted with hydrogen peroxide to a concentration of up to 3 proc. In some beauty salons, however, often stronger water is used with a concentration of do 6 proc. Admittedly, this allows the procedure to be carried out faster, but it causes drying of the hair and gradual chipping. So it's good to ask your beautician, what water (concentration) uses to prepare henna and ask for the right one.
Another activity, which is worth paying attention to, it's washing off the paint. It has to be done very delicately. Otherwise, the eyelashes may be mechanically damaged.