Is it permissible for a veiled woman (Niqabi) to uncover her face before a male dermatologist for acne treatment, given the unavailability of a female specialist in clinics affiliated with her father, and her financial inability to afford private clinics?

If a woman cannot find a female doctor to treat her face, or if she finds one but at an exorbitant cost, then there is no sin upon her in uncovering her face to a male doctor for treatment, provided that a mahram or another woman is present to negate khalwa (private seclusion).