The effects of the menstrual cycle on the skin.

The menstrual phase is, by definition, the period of menstruation, and the first day of menstruation is considered the start of the menstrual cycle. This is a 4 to 8 day period during which the lining of the uterus (uterine mucosa or endometrium) breaks down and is expelled in the form of bleeding of varying intensity (from 6 to 70 mL). This typically occurs every month except during pregnancy and after menopause.

What happens at the skin level?

With no pregnancy reported, the levels of oestrogen and progesterone plummet to their lowest. The skin then becomes more sensitive, prone to inflammatory reactions and drier with a weakened skin barrier. Moreover, due to the drop in hormone levels, blood circulation slows down, giving the skin a duller complexion. Indeed, the low level ofoestrogen could explain this phenomenon. It has a decisive influence on the quality of the skin: it promotes better wound healing, collagen production, skin hydration, improvement of the barrier function and an increase in skin thickness.

This second stage, the follicular phase, is dedicated to preparing for ovulation by producing the follicle-stimulating hormone (FSH) from the pituitary gland (a small region located at the base of the brain), which will induce the growth of numerous follicles (between 3 to 30 follicles): each follicle contains an egg. As the pre-ovulation phase continues, the level of FSH decreases: at this stage, only one follicle continues to develop and begins to produce oestrogens, while the others degenerate. When the oestrogen has reached its peak, this will trigger the release of the egg (ovulation). Indeed, the influx of oestrogen causes a significant rise in another hormone: the luteinising hormone (LH) produced by the pituitary gland. It is this hormone that leads the ovary to release a mature egg. In a typical 28-day cycle, ovulation usually occurs around the 14th day.

What happens at the skin level?

Under the influence of oestrogens, the skin generally radiates and maintains good health. They keep it supple, elastic, smooth and thick, by contributing to the natural production of collagen and elastin fibres, hydrated by stimulating the production of hyaluronic acid which helps skin cells retain water, and radiant by activating the blood microcirculation. Furthermore, at high concentrations, oestrogen would prevent the stimulation of the sebaceous glands and therefore the production of sebum, although the mechanism remains somewhat unclear.

The luteal phase is the final stage of the cycle. The ruptured dominant follicle, which has led to ovulation, will decompose into the corpus luteum, which secretes an increasing amount of progesterone, while the levels of FSH and LH decrease. The purpose of this hormone is to strengthen the uterine mucus in preparation for a potential implantation of the egg in case of fertilisation. In the event of pregnancy, the body will then produce the hormone human chorionic gonadotropin (HCG), which is detected by pregnancy tests. In the absence of pregnancy, the corpus luteum atrophies and hormone levels gradually decrease until the onset of menstruation and the start of a new cycle.

What happens at the skin level?

During this phase, the level of oestrogen drops sharply, while progesterone and androgens (testosterone) increase, leading the sebaceous glands to produce more sebum. The skin then becomes noticeably oilier, shinier and glossier than usual, the pores tend to dilate and clog, thus promoting the appearance of comedones, and the skin can develop into acne in the days preceding menstruation. One could even refer to this ashormonal acne for those who have a significant skin eruption during this period of the cycle. It's worth noting that the more androgens that bind to the receptors of the sebaceous glands, the greater the sebum production. One theory would be that the low level of oestrogen is not sufficient to exert its "anti-sebum" effect, thus allowing the androgens to act and create an environment conducive to the development of Cutibacterium acnes.

Many other factors can influence the oiliness of the skin (amount of sebum secreted) such as genetics, excessive sun exposure, inappropriate use of cosmetic products...