You cut out junk food. You started drinking more water. You added a new cleanser. And yet your skin still breaks out, especially when work piles up or a big deadline looms. It’s one of the most frustrating cycles in skincare, namely, you do everything “right,” and your skin still doesn’t cooperate.
Here’s what most conventional advice misses. Acne is rarely caused by a single factor. It’s almost always the result of overlapping biological processes, and research is starting to show that three major contributors – in addition to acne bacteria and hormonal imbalance - are sugar, dairy, and stress. Even more recent research shows that GLP-1 weight loss drugs can also trigger more acne, especially in women. Each works through its own distinct pathway to trigger breakouts, but all three converge on the same root mechanism, i.e., chronic, low-grade inflammation.
The emerging science on the gut-skin axis adds another layer to this picture. What you eat doesn’t just affect your blood sugar or cholesterol levels. It shapes the microbial community in your gut, which, in turn, communicates directly with your immune system and your skin. This means that sugar, dairy, and stress can all ripple outward in ways that extend far beyond a single pimple.
So, which is actually worse for your skin: what you eat or how you feel? The honest answer is nuanced and understanding it is the first step toward doing something about it.
How Sugar Triggers Acne
When you eat sugar or refined carbohydrates such as white bread, soda, candy, pastries, even “healthy” fruit juices, your blood sugar spikes rapidly. Your pancreas responds by releasing insulin to bring it back down. But that insulin surge doesn’t just manage your blood sugar. It also activates a hormonal cascade that directly affects your skin. [1] [2]
Insulin stimulates the production of insulin-like growth factor 1 (IGF-1), a hormone that tells your sebaceous (oil) glands to produce more sebum. More sebum means more of the fuel that acne bacteria thrive on. At the same time, IGF-1 promotes the growth of skin cells lining the inside of pores, which increases the likelihood of a blockage. The result is a pore that’s plugged from the inside and overfilled with oil, the classic recipe for a breakout.
Research consistently supports this mechanism. A 2025 systematic review of 20 studies found that low-glycemic dietary interventions such as specifically reducing high-sugar and refined-carb foods, led to measurable reductions in acne severity. Studies on participants who switched to a low-glycemic diet showed improvements in both the number of lesions and their overall inflammatory grade.
High-sugar diets also promote systemic inflammation by triggering the release of pro-inflammatory cytokines which are signaling proteins that keep your immune system in a state of low-level alert. On the skin, this translates to pores that more quickly become red, swollen, and painful when they get blocked.
The Dairy-Acne Connection: Hormones and More
Dairy’s relationship with acne is more complex than sugar, but no less real. Multiple large studies and meta-analyses have found a consistent association between milk consumption and increased acne risk, observed across whole milk, skim milk, and low-fat milk. [1] [2]
The primary mechanism involves the proteins naturally present in cow’s milk. Whey and casein, the two main proteins in dairy, are designed to help young calves grow quickly. When humans consume them, they stimulate a hormonal response that’s quite powerful, i.e., the body releases IGF-1, the same growth factor triggered by sugar and insulin. This creates a double effect for people who eat both high-sugar foods and dairy, namely, both are separately driving up IGF-1, and the skin bears the brunt of it.
Milk also contains naturally occurring hormones from the cows that produce it, including estrogens and androgens. These can interact with the body’s own hormonal balance, particularly in adolescents whose hormones are already in flux. Additionally, whey protein has been shown to raise insulin levels independently of sugar intake, which is why athletes using whey protein supplements sometimes report unexpected acne flares even when their diets are otherwise clean.
Not all dairy products seem to carry equal risk. Cheese, butter, and plain yogurt appear less consistently linked to acne in the research, possibly because they contain less whey and lactose, or because fermented dairy may carry offsetting benefits for the gut microbiome. The most robust associations in the literature are linked with milk, particularly skim milk.
GLP-1 Drugs and Health
GLP-1 drugs like Ozempic and Wegovy work by mimicking a hormone your body naturally releases after eating. They slow digestion, reduce appetite, and most important when it comes to one’s skin, lower insulin levels and reduce chronic inflammation throughout the body. Since high insulin and inflammation are two of the biggest drivers of acne, many people report clearer skin as a side effect of taking these medications.The connection to acne runs deeper through a molecule called “IGF-1” (insulin-like growth factor 1). IGF-1 is produced largely in response to insulin spikes, and it directly stimulate the skin’s oil glands to overproduce sebum and causes skin cells to turn over too rapidly, both of which represent the hallmarks of acne formation. By smoothing out one’s insulin levels, GLP-1 drugs tend to bring IGF-1 down as well, which can in turn calm oil production while reducing clogged pore formation at a hormonal level. [5] [6]
All this to say that the picture is not entirely rosy. Rapid weight loss, the goal associated with using such drugs, can cause one’s face to lose volume and elasticity which at times leaves skin looking looser and more aged, a phenomenon known as “Ozempic face”. Nutritional deficiencies from reduced appetite can also dull skin tone and slow its natural repair processes. So while GLP-1 drugs may genuinely help with acne and skin oiliness, their broader effects on skin appearance involve real trade-offs worth considering.
Stress, Cortisol, and the Sebum Surge
While stress-related acne works through a completely different biological pathway, it ends up in the same place. When you’re under psychological or physical stress, the hypothalamic-pituitary-adrenal (HPA) axis activates, ultimately triggering the adrenal glands to release cortisol, the body’s primary stress hormone. [3] [4]
Sebaceous glands in the skin have direct receptors for cortisol and corticotropin-releasing hormone (CRH). When these hormones bind to those receptors, the glands increase sebum production, sometimes dramatically. Research on human sebocyte cultures has documented how CRH directly stimulates oil production in sebaceous gland cells, providing a clear “cellular mechanism”, i.e., biological proof for why stress makes skin oilier.
But cortisol doesn’t just drive oil production. It suppresses ceramide formation in the skin, thereby weakening the skin’s protective barrier and making it more vulnerable to bacterial invasion. It also amplifies the release of inflammatory cytokines (signals), putting the immune system into a hair-trigger alert state. And research on wound healing consistently shows that elevated cortisol levels delay skin repair, meaning that stress breakouts don’t just happen more easily, they stick around longer.
One of the more confusing aspects of stress acne is the time lag. The cortisol-to-breakout window is typically two to seven days, meaning that the pimple erupting during your post-deadline recovery week is the direct result of the stress you’d already moved past. A peer-reviewed study confirmed a statistically significant correlation between stress severity and acne severity across a group of female medical students, validating what patients have long reported anecdotally.
The Common Thread: Inflammation and the Gut-Skin Axis
Whether the trigger is sugar, dairy, weight loss GLP drugs, or stress, all three converge on one central mechanism, namely, chronic low-grade inflammation. Acne is not just an infected pore but an inflammatory disease. Research has confirmed that inflammation is present throughout the entire process of acne development, not just at the visible pimple stage. This is why anti-inflammatory interventions, whether dietary or otherwise, can have meaningful effects on breakout frequency and severity. [2] [4]
What’s increasingly clear is that a significant part of this inflammatory signaling is routed through the gut. The gut-skin axis describes the bidirectional communication pathway between the intestinal microbiome and the skin’s immune and barrier systems. When the gut microbiome is balanced and diverse, it helps regulate immune responses, keep inflammation in check, and maintain a healthy skin environment. However, when it is disrupted, i.e., out of balance, a state called gut dysbiosis, that inflammatory regulation breaks down.
Both diet and stress are powerful disruptors of gut microbial balance. A high-sugar, high-saturated-fat diet promotes gut dysbiosis, increases systemic inflammation, and raises IGF-1 and insulin levels through the mTORC1 pathway thereby directly stimulating sebum production and creating an environment where acne-causing bacteria like C. acnes can thrive. Stress similarly disrupts the gut microbiome via the gut-brain axis, reducing populations of beneficial bacteria and increasing intestinal permeability (commonly called “leaky gut”), which allows bacterial byproducts to enter the bloodstream and worsen whole-body inflammation.
A landmark 2025 study using a Mendelian randomization approach, one of the most rigorous study designs for establishing causality, found evidence of a causal relationship between gut microbial composition and acne. Higher abundances of certain bacterial phyla were associated with increased acne severity, while a more diverse gut microbiome appeared protective. This research opens the door to microbiome-targeted interventions as a legitimate component of acne management.
The practical implication: treating acne from the inside out means addressing not just what you put on your skin, but what you feed the ecosystem living in your gut.
What You Can Do About It
The good news is that all four triggers, i.e., sugar, dairy, GLP-1 drugs and stress are partially within your control. Here’s where to start:
• Reduce high-glycemic foods: Swap refined carbohydrates (white bread, sugary drinks, processed snacks) for lower-glycemic alternatives like legumes, whole grains, and vegetables. The American Academy of Dermatology has noted that small studies show meaningful acne reduction for participants on a low-glycemic diet.
• Experiment with dairy elimination: Consider removing milk for three to four weeks and monitoring your skin. If you see improvement, reintroduce slowly and observe for flares. Be cautious of dairy-free milk alternatives with added sugars, which can trigger the same insulin response.
• Add green leafy vegetables: Research suggests that high dietary folate intake is associated with reduced circulating Insulin-like Growth Factor 1 (IGF-1) levels. Folate acts through the one-carbon metabolism cycle, where sufficient levels can downregulate the expression of the IGF-1 receptor (IGF-IR) and inhibit its signaling pathway. [1, 2, 3, 4[BP1] ]. Folate is high in dark leafy greens like spinach, asparagus, legumes like lentils and beans, and peanuts. Animal products like liver and eggs also have folate.
• Actively manage stress: Stress management isn’t optional skincare advice, it’s a biological intervention. Research shows that patients who used relaxation training, biofeedback, and mindfulness techniques showed measurable improvement in acne compared to control groups. Even a consistent eight-hour sleep schedule reduces cortisol and supports skin repair.
• Support your gut microbiome: Incorporate fermented foods (plain yogurt, kefir, kimchi, sauerkraut) and prebiotic-rich foods (garlic, onion, asparagus, oats) into your diet o promote microbial diversity. Probiotic supplements with clinically studied strains are an additional option, particularly during periods of high stress or antibiotic use.
• Use targeted topicals: Niacinamide (vitamin B3) reduces sebum production and calms the inflammatory response directly at the skin surface, making it particularly useful during stress flares when cortisol is suppressing the skin’s natural defenses. Ceramide-based moisturizers help restore the barrier that both stress and inflammation wear down.
Myths and Facts
"Diet has nothing to do with acne."
This belief stems from flawed 1960s studies. Modern meta-analyses and randomized controlled trials consistently link high-glycemic diets and dairy consumption to increased acne severity.
"Stress acne only happens if you’re extremely anxious or burned out."
Even moderate, everyday stress such as work deadlines, poor sleep, constant low-level anxiety can chronically elevate cortisol enough to increase sebum production and slow skin healing.
"Skim milk is a safe swap since it’s lower in fat."
Research shows skim milk is actually more consistently associated with acne than whole milk, possibly because the fat in whole milk slows hormonal absorption, while skim milk’s higher glycemic impact drives a sharper insulin response.
"Probiotics are just a wellness trend with no real skin benefit."
A 2025 Mendelian randomization study established a causal relationship between gut microbial composition and acne. Microbiome-targeted interventions are now considered a legitimate therapeutic avenue by dermatology researchers.
FAQs
Is sugar or dairy worse for acne?
Both contribute, but through overlapping mechanisms. Sugar drives breakouts primarily through insulin and IGF-1 spikes. Dairy works through IGF-1 stimulation and naturally occurring milk hormones. People who consume both high-sugar diets and dairy simultaneously may experience a compounding effect. Individual sensitivity varies, which is why an elimination trial can be informative.
Can stress alone cause acne without any dietary triggers?
Yes. Cortisol and corticotropin-releasing hormone (CRH) directly stimulate sebaceous glands to overproduce oil, suppress ceramide synthesis in the skin barrier, and promote systemic inflammation, all of which can drive breakouts independently of diet.
How does the gut microbiome actually affect my skin?
Through what researchers call the gut-skin axis, the intestinal microbiome communicates with the immune system and influences systemic inflammation. When the gut microbiome is disrupted by poor diet or stress, it can increase intestinal permeability (leaky gut), allowing bacterial byproducts into the bloodstream and amplifying the inflammatory signals that contribute to acne.
How long does it take to see results from cutting out sugar or dairy?
Most elimination studies run three to four weeks before meaningful changes in acne lesion counts are observed. Hormonal and inflammatory pathways take time to recalibrate, so short trials of less than three weeks may underestimate the true impact.
Are there specific probiotic strains that help with acne?
Research is ongoing, but Lactobacillus and Bifidobacterium species have shown the most consistent evidence for reducing systemic inflammation. Fermented foods like plain yogurt (without added sugar), kefir, and kimchi naturally contain these strains and support gut microbial diversity.
Conclusion
Sugar, dairy, and stress don’t cause acne in isolation, but rather, they each feed the same underlying fire, namely, chronic inflammation, hormonal dysregulation, and a gut microbiome knocked off balance. The question of which is “worse” misses the point. For most people with persistent breakouts, all three are contributing to some degree, and addressing only one while ignoring the others will produce limited results.
The most effective approach to acne is one that works on multiple levels simultaneously: reducing the glycemic load of your diet, testing dairy sensitivity, actively managing chronic stress, and supporting the gut-skin axis through diet and targeted supplementation. Clear skin isn’t just about what you put on your face. It’s the external expression of what’s happening in your body’s internal environment.
Call to Action
Codex Labs offers the carefully curated SHAANT ACNE SYSTEMS, formulated without hormone-disrupting preservatives, pore-clogging ingredients, or common irritants, and designed to target acne both at the surface (outside) and at its root (inside). Codex tackles the root cause of acne with its dietary supplements that help support the gut-skin axis, such as the probiotic-containing, gut microbiome-supporting SHAANT CLEAR SKIN, as well as the skin/mind calming SHAANT SKIN DE-STRESS supplement specifically formulated for those suffering from hormonal acne. Both supplements provide anti-oxidants to help improve systemic inflammation.
When it comes to the skin’s surface (outside), there is the SHAANT BALANCING FOAMING CLEANSER that not only cleanses acne-prone skin, but does so in a soothing, oil-reducing, microbiome-friendly manner. For those looking to gently, yet effectively, unclog their pores there is the SHAANT PORE PURIFYING ACNE FACE SCRUB with 2% salicylic acid and jojoba oil grains to gently remove impurities (dirt, oil, and dead skin cells) without stripping moisture or lipids (oil) from the skin barrier, keeping it healthy and happy. And, for those aesthetically annoying pimples, there’s the SHAANT SPOT HERO, a gentle pimple spot treatment with 5% colloidal sulfur that helps to: shrink and dry out pimples, reduce redness, and prevent acne pitting. The SHAANT ACNE SYSTEMS address all three sides of the acne triangle, i.e., diet, stress, and the skin barrier. It’s what we at Codex like to call our integrative, inside-outside approach to acne treatment. Explore the full range at codexlabscorp.com.
References
[5] https://www.verywellhealth.com/weight-loss-drugs-acne-11711085
