If a fasting person undergoes waxing or epilation for the removal of body hair, the fast is not invalidated. This is because the fast is invalidated by eating, drinking, or engaging in sexual intercourse. Removing body hair, whether by oneself or by another, does not fall under any of these categories and therefore does not invalidate the fast.
However, a related matter should be noted. If a woman has waxing performed by another woman, she must not expose the area between the navel and the knees, as this constitutes a woman’s private area (ʿawrah) in relation to another woman. It is not permissible to look at this area, nor is it permissible to touch it in a state of nakedness.