In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
If you are a female, there is no harm in going to a female skin specialist as long as she is professional and has questionable moral integrity. Religious differences do not matter. The Prophet (peace be upon him) and his companions made use of the services of people of integrity, notwithstanding their religious affiliations.
However, if you are a male, you should prefer a male specialist unless you have no choice and your condition is so severe that you are in dire need of such a treatment.
Almighty Allah knows best.