What Causes Acne in Adults? 6 Triggers You Might Not Know About

If you thought acne was a skin condition purely reserved for adolescents — this couldn’t be further from the truth. Globally, adult acne affects 1 in 5 individuals aged 25 to 39. 

In Australia alone, nearly half of men and women experience acne well into their 30s — making it one of the most common skin concerns we see in clinic. Despite the growing body of research on the topic, it remains one of the most misunderstood skin conditions.

Adult acne is the result of a complex mix of factors, ranging from hormones to genetics, and more. In this article, we break down exactly what acne is and what causes acne in adults. 

Before we get into what causes acne in adults, let’s briefly touch on what acne actually is. In its simplest explanation, acne is an inflammatory skin condition that occurs when hair follicles become clogged with sebum and dead skin cells. Adult acne — also known as post-adolescent acne or hormonal acne — refers to men and women aged 20 and over. 

Let’s delve a little deeper. Your skin consists of pores, which are connected to oil glands that produce something called sebum (your skin’s natural oil, which has a waxy consistency). When your skin is functioning as it should, sebum travels from the oil gland up through the pores and onto the skin’s surface, where it keeps your face moisturised. 

However, when dead skin cells and excess oil become trapped together, they can clog your pores, leaving nowhere for the oil to escape. Once blocked, this creates a perfect breeding ground for the bacteria that naturally lives on your skin to multiply, causing inflammation marked by swelling, redness, and sensitivity. What happens next determines the varying types of acne that can develop. 

[Read Full Article: Know Your Skin: The Beginner's Guide to Understanding Acne]

Now that we’ve covered what acne is and how it forms, let’s take a closer look at what causes acne in adults. There are four known factors directly linked to acne:

1. Excess oil production

2. Clogged pores

3. Bacteria 

4. Inflammation

However, several lifestyle and genetic components may also contribute to this. Here are some of the more common reasons you may be experiencing adult acne:

Among the most common causes is the skin producing too much sebum. Oil plays an important role in skin health — it’s made up of triglycerides, fatty acids, and esters, which work together to keep your skin moisturised, transport antioxidants, and help to safeguard your skin against UV damage. However, too much of anything is rarely a good thing, and oil is no exception. When excess sebum is produced, it can meddle with follicular keratinisation, resulting in blocked pores. Several factors can contribute to excess oil production, including those outlined below.

Hormonal acne can occur when someone experiences a fluctuation in estrogen, progesterone, and testosterone. While it can affect men and women from early teens through to adulthood, it’s more prevalent in women. In fact, it’s believed that roughly 50% of women aged 20-29, and 25% of women aged 40-49 have experienced acne

Here’s why: women generally experience more hormonal fluctuations than men due to their menstrual cycles, as well as pregnancy and menopause. Discontinuing certain medications, such as hormonal birth control, can also disrupt hormone levels and trigger breakouts.

When hormones fluctuate, they can signal the sebaceous glands to produce more sebum, causing inflammation and pimples to form. 

There has always been an interesting debate surrounding the connection between diet and acne. While some researchers believe things like oily foods and chocolate contribute to breakouts, others believe this to be a myth. However, what the evidence does suggest is that certain foods can spike blood sugar and insulin levels, causing inflammation — which can subsequently result in acne.

A study conducted between November 2018 to July 2019 compared dietary surveys from over 24,000 participants with current acne, past acne, or no history of acne. The study found a link between current acne and the consumption of high fat foods (including milk and meat), high-sugar foods and beverages, and a diet rich in both. Participants with current acne were 54% more likely to consume a diet with these foods compared to those who’d never experienced acne. 

Unfortunately, some contributing factors are inherited, and largely out of our control. It's worth noting, however, that while acne does often run in families, there is no single acne gene. So how exactly can it be passed down?

• Your genetics can dictate your immune response — Research shows that genetics often influence how well your immune system responds to fighting off the bacteria that promotes acne, P. acnes. For example, when certain genes have increased activity, such as the interleukin family (particularly IL-1B), it is shown to create a heightened inflammatory response, resulting in severe acne.

• PCOS can be hereditary — Polycystic Ovary Syndrome (PCOS) is a hormonal condition that can run in families. As discussed above, conditions that encourage hormonal fluctuations, like PCOS, can trigger acne.

• A family history of acne can cause acne resistance — While not strictly genetic, several studies have found that a child is more likely to experience acne if one or both parents had it. It is believed that follicles becoming acne resistant in adulthood can be passed down the family line. 

While stress could also fall under the hormones category, it deserves a section of its own. When you're stressed, your body releases cortisol — commonly known as the "stress hormone." In small, controlled amounts, cortisol is healthy and normal. However, when it floods the body, it stimulates the sebaceous glands to produce more oil, increasing the likelihood of acne for all the reasons outlined above. Elevated cortisol is also thought to slow skin cell turnover, which can clog pores with dead skin cells and bacteria, leading to inflammation and breakouts.

Chronic stress also triggers low-grade inflammation in the body — an immune response that can further contribute to acne.

Lastly, research indicates that acne wounds, as with all wounds, heal at a much slower rate when someone is experiencing stress. This may result in longer breakouts, and even more severe acne as your stress increases.

If you've ever wondered what causes acne in adults that seems to flare with no obvious external trigger, chronic stress is often the overlooked answer.

You might recall us mentioning the four known factors that cause acne. One of the four is clogged pores, which can occur when comedogenic ingredients trap oil, bacteria, and dead skin cells inside the pore.

Comedogenic ingredients include ingredients such as certain oils — like coconut oil, almond oil, olive oil, etc., — cocoa butter, lanolin, and more. By clogging your pores, this creates the perfect breeding ground for acne-causing bacteria to multiply.

Additionally, products containing artificial fragrances can irritate the skin and cause inflammation — another known contributor to acne. When selecting skincare, always look for products labelled non-comedogenic.

As we've explored, adult acne is rarely the result of a single factor — it's most often a combination of hormones, genetics, lifestyle habits, and the products you're using on your skin.

The good news? Many of these triggers are manageable. Whether it's adjusting your diet, reviewing your skincare routine, or seeking professional advice about hormonal imbalances, there are evidence-based solutions available.

If you're struggling with persistent breakouts, it's worth speaking with a dermatologist or skin-focused GP who can help identify your specific triggers and recommend a targeted treatment plan.