Your Scalp
Has a Cycle

Two hormones, two effects on the scalp

In the follicular phase (days 1–14), rising oestrogen extends the active growth phase of the hair follicle and tends to calm sebaceous gland activity. This is typically when the scalp feels most balanced.

After ovulation, in the luteal phase (days 15–28), progesterone takes over. Progesterone is a known stimulator of the sebaceous glands. For scalps already prone to oiliness, this can mean a measurably greasier scalp in the one to two weeks before menstruation.

“A bad hair day before your period is not imagined. But it is not universal — and that distinction matters.”

What the research actually shows

Clinical studies measuring scalp sebum across the cycle have found that oil production tends to peak in the premenstrual and menstrual period, with the lowest levels occurring around the second week of the cycle. One frequently cited study found that while women reported more bad hair days around menstruation, this did not always correlate with measurably higher scalp sebum. Perception and biology do not always move together.

What this means in practice

If your scalp feels oilier in the week before your period, you are not imagining it. What can help is adjusting how often you cleanse — not which product you use. Washing slightly more frequently with a mild, sulphate-free shampoo removes excess sebum without creating the over-cleansing cycle that harsh SLES-based shampoos trigger. An SCI + CAPB base allows for more frequent washing during hormonally oilier periods without compromising the scalp’s lipid balance.