Understanding the root causes of acne

Acne is often dismissed as “just a skin condition”, but for many people, it can affect confidence, relationships, social life and mental well-being.

And while conventional treatment often focuses on the skin itself, research increasingly suggests that acne may be influenced by much deeper factors, including hormones, gut health, inflammation, stress and nutrition.

As a nutritional therapist, I often see persistent breakouts as a sign that something deeper may be out of balance. For some people, this may be linked to hormones or blood sugar regulation, while for others it may involve inflammation, gut health or chronic stress.

Understanding these underlying patterns can help us move beyond simply suppressing symptoms and towards supporting long-term skin health.

What causes acne?

Acne is a chronic inflammatory skin condition affecting almost 10% of the global population. Although it is most common during adolescence, adult acne is becoming increasingly common, particularly in women.

Many women notice that their skin worsens at different points in their cycle, e.g. around ovulation or before their period. This suggests that hormonal fluctuations may play an important role. Acne is also associated with psychological distress, including increased rates of anxiety, low mood, social withdrawal and reduced self-esteem.

From a physiological perspective, acne develops when excess oil (sebum), dead skin cells and inflammation contribute to blockage within the pore. This creates an environment where inflammation can thrive.

Interestingly, our understanding of acne has evolved considerably in recent years. Acne was once thought to be primarily caused by Cutibacterium acnes (formerly P. acnes) bacteria. However, newer research suggests the picture is far more complex. Many strains of this bacteria may actually play a beneficial role in skin health, and acne sufferers do not necessarily harbour higher levels than those without acne.

This has shifted the conversation away from simply “killing bacteria” and towards understanding the wider internal factors that may be influencing skin.

Hormones and acne

Hormones are one of the most well-recognised drivers of acne. Androgens such as testosterone can increase sebum production, particularly when testosterone is converted into a more potent form called DHT (dihydrotestosterone). This may contribute to oilier skin and increased breakouts in some individuals. Conditions associated with higher androgen levels, such as PMOS, are also linked with increased acne prevalence.

Blood sugar regulation may play a role, too. Diets high in refined carbohydrates and sugar can increase insulin and insulin-like growth factor 1 (IGF-1), both of which may stimulate oil production and inflammatory pathways involved in acne. This is one reason why some people notice improvements in their skin when they focus on stabilising blood sugar levels through balanced meals and adequate protein and fibre intake.

Thyroid hormones also play a role in skin health, regulating cell turnover and sebum production. When thyroid function is suboptimal, the skin barrier can become compromised and slower to heal. The thyroid also influences gut motility, affecting constipation or diarrhoea depending on whether it is under- or overactive. This can affect toxin elimination, hormone balance and nutrient absorption, all of which may contribute to acne.

The gut-skin connection

One of the most interesting areas of acne research is the “gut-skin axis”, referring to the two-way relationship between the gut microbiome, immune system and skin health. The gut microbiome influences inflammation, immune signalling, nutrient absorption and even hormone metabolism, all of which may affect the skin.

Some studies suggest that people with acne may be more likely to experience gut dysbiosis, meaning an imbalance between beneficial and less beneficial bacteria. Alterations in the microbiome may also contribute to increased intestinal permeability, sometimes referred to as “leaky gut”, which may promote systemic inflammation. Although this area of research is still developing, it highlights the importance of looking beyond the skin itself.

In clinic, I often see clients whose skin worsens alongside digestive symptoms, chronic stress, disrupted sleep or blood sugar imbalance, even when their skincare routine has not changed.

Stress and inflammation

Stress is another major piece of the puzzle. Stress hormones such as cortisol and adrenaline may increase sebum production and influence inflammatory activity within the skin. Stress can also impact sleep, blood sugar regulation, digestion and hormone balance, creating multiple pathways through which it may affect acne.

Unfortunately, acne itself can also become a source of stress, creating a difficult cycle where psychological distress and skin symptoms continually reinforce one another. This is why a supportive and holistic approach can often be important.

Could diet be contributing?

There is currently no single food proven to “cause” acne, and triggers can vary significantly from person to person. However, research suggests that certain dietary patterns may influence acne severity in some individuals.

Diets high in refined carbohydrates, sugar and some forms of dairy have been associated with increased IGF-1 activity and greater acne severity in some studies. Food sensitivities may also contribute for certain people, particularly where there is an underlying inflammatory or gut-related component, although this is highly individual.

Rather than focusing on restriction, I generally encourage a nutrient-dense approach that supports inflammation regulation, blood sugar balance and skin barrier health.

Genetics

Genetics can also play a role in acne susceptibility, although it is important to emphasise that they do not determine outcomes on their own. Instead, they may influence how the body responds to certain internal and external triggers.

For example, some individuals may have genetic variations that affect hormone metabolism, inflammatory signalling, or how efficiently the skin responds to oxidative stress. Others may have differences in nutrient metabolism, such as vitamin A or zinc utilisation, which are important for skin health.  

Genetic predisposition does not mean acne is inevitable, but it may help to explain why some people are more sensitive to certain triggers than others.  

Nutrients involved in skin health

Healthy skin relies on a wide range of nutrients. Vitamin A and zinc are involved in skin repair and immune regulation, while omega-3 fats may help to regulate inflammatory pathways and support the skin barrier. Vitamins C and E also help to support the skin barrier, as well as provide antioxidant protection.

Fibre-rich foods are also particularly important, as they help to support a healthy microbiome and blood sugar balance. Foods such as legumes, oats, nuts, seeds, vegetables and whole grains can all contribute towards overall skin health.

Are probiotics helpful for acne?

Research into probiotics and acne is growing rapidly, although the evidence is not yet strong enough to make definitive recommendations.

Some probiotic strains appear promising, particularly those involved in supporting inflammation, barrier function, gut microbiome and the gut-brain axis. However, not all probiotics will work in the same way, as effects are likely to be strain-specific.

In some cases, focusing on prebiotic-rich foods, the fibres that feed beneficial gut bacteria, may be equally or even more important.

Functional testing: gaining a clearer picture

In some cases, it can be helpful to use functional testing to better understand potential drivers behind acne. Rather than looking at symptoms in isolation, these tests can offer additional insights into areas such as hormone patterns, nutrient status, gut health and inflammation.

This might include stool testing to assess aspects of the microbiome, blood testing to explore markers such as insulin regulation, inflammation or nutrient levels, and hormone testing, to look more closely at androgen balance and oestrogen metabolism. In some cases, more specialised testing can help to identify patterns that may not be obvious from symptoms alone.

Looking at the bigger picture

Acne is rarely caused by one single factor. For some people, hormones may be the primary driver, while for others, it may be stress, gut health, inflammation, nutrient status or blood sugar imbalance. Understanding these underlying patterns can help create a more personalised and sustainable approach to supporting skin health.

And while there is rarely a quick fix, if you're ready to move beyond symptom management and start exploring what's really driving your skin, working with a nutritional therapist can help you build a clearer, more personalised picture, and a plan that addresses the root.

References

Borzyszkowska, D., Niedzielska, M., Kozłowski, M., Brodowska, A., Przepiera, A., Malczyk-Matysiak, K., Cymbaluk-Płoska, A., & Sowińska-Przepiera, E. (2022). Evaluation of hormonal factors in acne vulgaris and the course of acne vulgaris treatment with contraceptive-based therapies in young adult women. Cells, 11(24), 4078. https://doi.org/10.3390/cells11244078 

Carmina, E., Dreno, B., Lucky, W. A., Agak, W. G., Dokras, A., Kim, J. J., Lobo, R. A., Ramezani Tehrani, F., & Dumesic, D. (2022). Female adult acne and androgen excess: A report from the multidisciplinary androgen excess and PCOS committee. Journal of the Endocrine Society, 6(3). https://doi.org/10.1210/jendso/bvac003 

Cros, M. P., Mir-Pedrol, J., Toloza, L., Knödlseder, N., Maruotti, J., Zouboulis, C. C., Güell, M., & Fábrega, M-J. (2023). New insights into the role of cutibacterium acnes-derived extracellular vesicles in inflammatory skin disorders. Scientific Reports, 13(1). https://doi.org/10.1038/s41598-023-43354-w  

Marasca, C., Ruggiero, A., Cacciapuoti, S., Fabbrocini, G., & Annunziata, M. C. (2023). Probiotic supplement combined with topical therapy in the treatment of mild to moderate acne: Results from an Italian single centre interventional study. Italian Journal of Dermatology and Venereology, 157(6). https://doi.org/10.23736/s2784-8671.22.07361-3 

Melnik, B. C. (2023). Acne transcriptomics: Fundamentals of acne pathogenesis and isotretinoin treatment. Cells, 12(22), 2600. https://doi.org/10.3390/cells12222600 

NICE. (2023). Acne vulgaris. National Institute for Health and Care Excellence. https://cks.nice.org.uk/topics/acne-vulgaris/ 

O’Neill, A. M., Cavagnero, K. J., Seidman, J. S., Zaramela, L., Chen, Y., Li, F., Nakatsuji, T., Cheng, J. Y., Tong, Y. L., Do, T. H., Brinton, S. L., Hata, T. R., Modlin, R. L., & Gallo, R. L. (2024). Genetic and functional analyses of cutibacterium acnes isolates reveal the association of a linear plasmid with skin inflammation. Journal of Investigative Dermatology, 144(1). https://doi.org/10.1016/j.jid.2023.05.029  

Rajkumar, J., Chandan, N., Lio, P., & Shi, V. (2023). The skin barrier and moisturization: Function, disruption, and mechanisms of repair. Skin Pharmacology and Physiology, 36(4), 174–185. https://doi.org/10.1159/000534136 

Reynolds, R. V., Yeung, H., Cheng, C. E., Cook-Bolden, F., Desai, S. R., Druby, K. M., Freeman, E. E., Keri, J. E., Stein Gold, L. F., Tan, J. K. L., Tollefson, M. M., Weiss, J. S., Wu, P. A., Zaenglein, A. L., Han, J. M., & Barbieri, J. S. (2024). Guidelines of care for the management of Acne Vulgaris. Journal of the American Academy of Dermatology, 90(5). https://doi.org/10.1016/j.jaad.2023.12.017 

Rocha, M. A., & Bagatin, E. (2018). Adult-onset acne: Prevalence, impact, and management challenges. Clinical, Cosmetic and Investigational Dermatology, Volume 11, 59–69. https://doi.org/10.2147/ccid.s137794 

Sánchez-Pellicer, P., Navarro-Moratalla, L., Núñez-Delegido, E., Ruzafa-Costas, B., Agüera-Santos, J., & Navarro-López, V. (2022). Acne, microbiome, and probiotics: The gut–skin axis. Microorganisms, 10(7), 1303. https://doi.org/10.3390/microorganisms10071303  

Schachner, L. A., Alexis, A. F., Andriessen, A., Berson, D., Gold, M., Goldberg, D. J., Hu, S., Keri, J., Kircik, L., & Woolery‐Lloyd, H. (2023). Insights into acne and the skin barrier: Optimizing treatment regimens with ceramide‐containing skincare. Journal of Cosmetic Dermatology, 22(11), 2902–2909. https://doi.org/10.1111/jocd.15946 

Shi, Z., Malfa, P., De Ponti, I., Yu, X., Lo Re, M., & Tursi, F. (2024). Investigating the impact of oral probiotic supplementation for Acne Management: A randomized controlled trial. Our Dermatology Online, 15(3). https://doi.org/10.7241/ourd.20243.1 

Tan, J. K. L., & Bhate, K. (2015). A global perspective on the epidemiology of acne. British Journal of Dermatology, 172, 3–12. https://doi.org/10.1111/bjd.13462 

Vasam, M., Korutla, S., & Bohara, R. A. (2023). Acne vulgaris: A review of the pathophysiology, treatment, and recent nanotechnology based advances. Biochemistry and Biophysics Reports, 36, 101578. https://doi.org/10.1016/j.bbrep.2023.101578