No, Sebum Does Not Cause Acne

Here’s what does.

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Ask the average skincare enthusiast what causes clogged pores — otherwise known as acne — and they’ll probably answer “sebum.” There are aestheticians and dermatologists and all sorts of online experts who’ll say the same thing. But it’s not true. It’s one of the biggest myths in the beauty industry and it’s sad, really.

As I once wrote in Nylon, “Our poor, sweet sebaceous glands did nothing to deserve this. Sebum — and I cannot stress this enough — does not cause acne.”

Sebum is a vital component of healthy skin. It’s the body’s built-in moisturizer, responsible for locking in hydration. It is integral to the acid mantle, a thin layer of the skin barrier that helps neutralize invading pathogens and stabilize the skin’s pH level. Sebum has “innate antibacterial activity” and can even have an anti-inflammatory effect on the skin. It is essential to the skin’s wound-healing response, and acts as a natural sun protector, too. Sebum is one of the most magical and precious skin care products in existence, and it comes out of your own pores.

So how did it get such a bad rap? It’s complicated. Sebum is involved in the proliferation of acne, but to borrow one of scientists’ favorite sayings, “correlation does not equal causation.” Sebum only contributes to acne if other factors are at play. (Think of it this way: “Oily skin” and “acne-prone skin” are two separate skin issues, right?)

The root cause or causes will differ from person to person, but the big one is hormonal imbalance. Sebum production is stimulated by testosterone and the “stress hormone” cortisol. An excess of either can lead to excess sebum, which can lead to clogged pores, which can lead to acne. In this sense, hormonal breakouts act as communications from the body (“We’re imbalanced in here!”).

Sluggish desquamation can lead to clogged pores, too. Desquamation is the skin’s process of self-exfoliation. Typically, skin cells will form, mature, and shed (through desquamation!) over the course of 28(ish) days. When they don’t shed, sebum can get “stuck” behind a wall of dead skin cells, et voila: acne. It’s not as simple as exfoliating those dead skin cells away, though. Dead skin cells are super important to the functioning of the skin barrier — they hold the skin’s Natural Moisturizing Factors, another part of the skin’s built-in system of hydration and moisturization, and provide a necessary layer of protection — and removing them may inadvertently cause more acne. It’s far more effective to support the skin’s inherent cycle of desquamation (which is a whole separate article).

Another culprit is a lack of linoleic acid, a critical component of sebum. As an Omega-6 fatty acid, linoleic acid is considered an “essential fatty acid,” meaning it’s essential to bodily functions — in addition to skin health, it contributes to brain health and heart health — but the body cannot produce it on its own. Without enough linoleic acid, sebum becomes thick and “sticky” and thus, more likely to clog pores.You can add linoleic acid directly to your face with skin care ingredients like watermelon seed oil and chia seed oil, but studies note it also “must be obtained from the diet.” (Nuts and seeds are excellent sources.)

While we’re on the subject of diet… yup, the food you eat affects your face. I’ll let science handle this one: “Studies have demonstrated that increased consumption of dietary fat or carbohydrate increases sebum production and modifications to the type of carbohydrate can also alter sebum composition,” reads a 2011 paper on the role of sebum in the development of acne. “Typical western diet, comprised of milk and hyperglycaemic foods, may have potentiating effects on serum insulin and insulin-like growth factor-I levels, thereby promoting the development of acne.” Basically, dairy and sugar can play a part in the proliferation of pimples; but really, any food that your unique body is sensitive to can cause inflammation. (Almonds are a trigger for me.)

Acne goes beyond diet, though. It’s also tied to gut health — and how researchers know this is pretty freakin’ fascinating. The gut and skin develop from the same bit of embryonic tissue in utero, and the two stay linked forever. The gut microbiome affects the skin’s immune response and inflammation levels, and is responsible for synthesizing vitamins that are essential to skin health, including biotin and vitamin K.

There’s even evidence to suggest the gut microbiome influences the skin microbiome, which is the skin’s first line of defense against acne-causing bacteria. This face-dwelling microbiome is made up of billions of microorganisms, including bacteria, all living in harmony. One such strain of bacteria is p. acnes, which takes a lot of blame for breakouts, but get this: P. acnes appears in clear pores, too. In fact, it’s necessary for a healthy microbiome. “P. acnes hydrolyses sebum into free fatty acids and propionic acid, aiding in proper skin barrier function,” explains chemist and skin care formulator Marie Veronique Nadeau in her book The Acne Answer. Problems — and by problems, I mean pimples — only arise when p. acnes is met with a clogged pore (see: all of the above), which then causes inflammation.

The p. acnes piece of the puzzle is particularly interesting, as recent studies into isotretinoin (Accutane) claim the drug “modifies the skin microbiota,” theoretically making it a more effective acne treatment. But the “modification” these studies point to is the near-elimination p. acnes — which, again, just like our misunderstood friend sebum, actually strengthens the skin barrier and only causes acne if outside factors are involved.

There are plenty of other acne instigators: not getting enough vitamin D, the overuse of skin care products, the overuse of harsh skin care products, immune response, intolerances, and more. But you know what’s not on that list, and will never be on that list? Sebum.

As dermatologist Dr. Aanand Geria so perfectly put it when I interviewed him for Nylon: “We need to change our attitude toward sebum, because vilifying it almost always makes skin worse in the long run.”