Apparatus and methods for treating skin conditions that deliver high frequency energy to a patient's tissue. The apparatus has a treatment tip configured to be removably connected with a handpiece, a conduit inside the handpiece, and a flow control valve inside the handpiece. The treatment tip has an electrode configured to deliver the high frequency energy to a region of the tissue. A lumen of the conduit is configured to transfer a heat transfer fluid from the handpiece to a flow passageway in the treatment tip. When the treatment tip is removed from the handpiece, the flow control valve is configured to occlude the lumen of the conduit for reducing leakage of the heat transfer fluid from the handpiece.