Certain subsets of hormonal birth control can improve hormonal acne during treatment. "Combined hormonal contraceptives are birth control methods that contain estrogen and progestin," says King, noting that these often come in forms such as pills, patches, and rings. “Birth control pills that contain these two hormones are often helpful for hormonal acne because the estrogen in them can suppress androgen production by the ovaries and increase a protein called sex hormone-binding globulin in the blood. This protein binds free testosterone in the bloodstream, leaving less testosterone available to cause sebum production and acne. "
You see, sex hormones have some notable effects on our skin. As King noted, estrogen decreases sebum production (and increases collagen and elastin production), while testosterone increases sebum production. If you are genetically predisposed to acne, any increase in sebum production can lead to breakouts.
When you stop using these forms of birth control, the hormonal acne you are experiencing is simply your skin responding to the lack of estrogen used in birth control as well as to the resurgence of testosterone.
“If you stop taking oral contraceptive pills, you lose all benefit to the acne they are providing, and acne can get worse as a result. Also, hormone levels go through an adjustment period a few months after stopping OCP, and acne can particularly flare up during this window, ”says King.