Why Is My Face So Oily?

The search question "why is my face so oily?" mostly has the same answer: hormones, age, sex and temperature, which are things a cleanser does not touch. DermNet says sebum production is under the control of sex hormones, rises up to fivefold in men at puberty, and declines with age, particularly after menopause in women.

The claim most often added to that is that washing, or washing too much, makes it worse. Our article on skin barrier repair already treated that as unsupported rather than disproven, and this article sets out what the sources do show about what drives oil, what has measurably lowered it, and when oiliness is a clue to something else. It covers cause, not product. It evaluates claims, and it does not tell you what to use.

What You Can and Cannot Change

Oil is not a defect to be removed. DermNet says sebum reduces water loss from the skin surface and helps protect against bacteria and fungi, so the question is not how to remove it but why a given face makes more of it than another. Many readers searching for oily skin are really asking that.

DermNet lists the things that alter sebum output, and they sort into two groups. The first group is not changeable by skin care: sex hormones (androgens), age, sex, and disorders of the pituitary, adrenal, ovarian or testicular glands. The second is changeable only by medicines: oestrogens such as the combined oral contraceptive pill, antiandrogens such as cyproterone acetate and spironolactone, and vitamin-A derivatives such as isotretinoin reduce sebum, while testosterone increases it.

The sources opened give no heritability figure for oiliness, so "genetics" is plausible but unquantified here. A large Chinese cohort summarised in the same review found sebum on the forehead higher than on the forearm, higher in males than in females at every age, and a peak around age 40 in females and 50 in males, which the review says may reflect ethnic differences.

How oily you think you are is only loosely tied to how much sebum is measured. In a study of 71 healthy volunteers that compared the Baumann skin-type questionnaire with instruments, the oily-versus-dry score correlated with measured sebum at r = 0.299, which the authors call poor, and not significantly with hydration or water loss. A face that looks shiny at 3 pm may be producing a normal amount, or a dry-feeling face may be producing more than it feels like.

Androgens and the Gland

DermNet says androgens, chiefly testosterone and dihydrotestosterone, stimulate sebaceous gland cells, and that enzymes in the skin make them more active. A review of ageing in the sebaceous gland adds that sebum is relatively low in children and begins to rise with the adrenal androgens at adrenarche and further at puberty, that sebum in women begins to decline with menopause, and that in elderly males it stays almost unchanged even at 80.

DermNet says only that production declines with age, particularly after menopause. The two descriptions differ on men: one says a decline, the other near-constancy to 80. The sources do not resolve it.

The glands are densest where oil complaints are. DermNet puts up to 400 to 900 glands per square centimetre on the forehead, chin and mid-back, with fewer elsewhere, and none on the palms and soles.

Our article on sebaceous hyperplasia covers a different late-life change: the ageing review reports glands enlarging in older, light-exposed skin, which it links to falling androgens, while output is low.

Heat, Humidity and Season

Heat raises output in the studies opened. In a year-long study that measured sebum at five facial sites in the same volunteers, summer was the highest sebum-secreting season (abstract), the forehead, nose and chin secreted more than the cheeks, and seasonal variation was found in both the T-zone and the U-zone. The authors propose that a mismatch of skin type between the zones in more than two seasons is close to what people call combination skin. Our article on combination skin covers that pattern.

Our article on acne in hot, humid climates covers the humid-climate side. The sources opened for this article did not separate temperature from humidity for sebum itself.

Why Washing More Does Not Reduce It

Washing removes sebum that is already on the surface. Whether it changes how much the gland makes is a separate question, and no source opened shows that it raises output. The most-cited objective data are a scalp shampoo wash-frequency study in Asian adults without scalp disease, where a daily wash was superior to a weekly one on all end points and no objective detrimental effects were found. It is a scalp study, not a face study, and two of its authors are at a consumer products company. Applied to the face, the honest status of the "rebound oil" idea is unsupported, not disproven, which is how the library already states it.

What over-washing reliably does is a different problem: barrier damage, which leaves skin tight and flaky. Our article on choosing a cleanser for oily skin covers that side.

What Has Measured Sebum Reduction

Per DermNet's list above, the agents that reduce sebum are systemic: oestrogens including the combined pill, antiandrogens (cyproterone acetate, spironolactone) and isotretinoin. All of these are prescription decisions, and their place is with a clinician.

The best-known topical with sebum measurements is 2% niacinamide. In two trials (abstract), a double-blind placebo-controlled study of 100 Japanese subjects found the sebum excretion rate significantly lower at two and four weeks, while a 30-person split-face study in Caucasian subjects found casual sebum level reduced at six weeks but the excretion rate not significantly reduced. The authors conclude it may be effective in lowering the rate in Japanese individuals and the casual level in Caucasian individuals. The abstract does not state who funded the trials, and the evidence is two small studies in different populations with different results.

How recently you washed your face is not on either list.

The Figure Audited: "Oily Skin Ages More Slowly"

Verdict: unproven. No source opened compared ageing in oily and dry skin. Findings:

1. The belief rests on two trends that move together. In a cross-sectional study of Chinese women, wrinkles increased and sebum secretion decreased with age, and the stable-ageing group had the lowest sebum and the most wrinkles, stains, blackheads and pores. Two things changing with time do not show that more oil slows the first.
2. The ageing review links dry, rough skin to falling sebum and lipids, and says photoageing changes sebum composition and goes with gland enlargement in light-exposed skin. That ties lipids to dryness and roughness, not to wrinkle rate.
3. Wrinkles are driven by other things. Our article on SPF and wrinkles covers UV, the main outside cause, and nothing opened suggests oil offsets it.
4. Oil has costs. DermNet lists increased sebum production among the causes of enlarged pores, and the same sebum is part of acne.

Limits: the Chinese study is cross-sectional and in women; no study opened grouped people by oiliness and followed or compared wrinkles. The idea is not refuted. It is not demonstrated.

When Oiliness Is a Clue

"Oily skin dermatologist" is a common search, and DermNet gives a reason a clinician is useful. It lists pituitary, adrenal, ovarian or testicular disorders as able to increase or reduce sebum, prolonged starvation as reducing it, and Parkinson disease as increasing it.

That is a list of possibilities for a clinician to consider, not a way to diagnose oneself. A sudden change in oiliness, oiliness with other changes, or oiliness that comes with acne that does not respond to treatment are the situations in which asking is reasonable.

Conclusion

The answer to "why is my face so oily?" is that hormones, age, sex and heat set the baseline, the cheeks make less than the forehead, and the best objective data find no sign that washing raises output. Medicines lower sebum measurably, a 2% topical has two small trials with mixed results, and nothing opened shows oily skin ages more slowly.

If you want to know whether a change is real, photographing your forehead and nose in the same place and light at the same time of day, in an album or in an app like Skinic, shows more than your impression of shine. For sudden changes or acne that is not responding, ask your own clinician.