{"id":10540,"date":"2026-08-20T10:43:56","date_gmt":"2026-08-20T01:43:56","guid":{"rendered":"https:\/\/kojihifu.com\/english\/?p=10540"},"modified":"2026-08-20T10:43:57","modified_gmt":"2026-08-20T01:43:57","slug":"adult-acne-rosacea-gut-tokyo","status":"publish","type":"post","link":"https:\/\/kojihifu.com\/english\/adult-acne-rosacea-gut-tokyo\/","title":{"rendered":"Adult Acne and Rosacea in Tokyo: The Gut-Skin Connection"},"content":{"rendered":"

By Dr. Jun Karibe, MD<\/strong> \u2014 BIOTOPE Clinic Shirokanedai, Tokyo \u00a0\u00b7\u00a0 Reviewed August 2026<\/p>\n

A patient in her late thirties books an aesthetic consultation. Her presenting complaint is adult acne<\/strong> \u2014 jawline breakouts that appear a week before her period, disappear briefly, and return in a slightly new location the following month.<\/p>\n

Her skincare shelf is populated by well-chosen Japanese and Korean products. She has completed rounds of topical adapalene and clindamycin from a dermatologist. A course of oral doxycycline helped for three months and then stopped helping. She has also tried a Vitamin C infusion series and monthly laser toning. She is doing everything the internet suggested. Her skin is somewhat better than baseline and quite far from where she wants it to be.<\/p>\n

A second patient, in her mid-forties, comes in for what she calls “the redness.”<\/strong> Her cheeks flush after a glass of wine, after a hot bath, after spicy food, and \u2014 increasingly \u2014 after nothing in particular. Small papules have started to appear on the central face. She has been treating this as sensitive skin for years. Two dermatologists have prescribed metronidazole gel and azelaic acid, both of which help modestly and neither of which resolves the problem. She has arrived at our clinic because a friend mentioned that BIOTOPE CLINIC<\/strong> looks at nutrition alongside skin.<\/p>\n

Both patients are doing the topical work correctly. In both cases, the topical work will only take them about seventy percent of the way. The remaining thirty percent \u2014 the part that makes the topical protocols actually last \u2014 lives in the gut, in the hormones, in the diet, and in the systemic inflammation that neither the tube of cream nor the laser can reach. This article is a practical guide to that remaining thirty percent for adults living in Tokyo who have adult acne, rosacea, or the increasingly common overlap of the two.<\/p>\n

Why adult acne is not teenage acne<\/h2>\n
\"adult<\/figure>\n

Adolescent acne<\/strong> is largely driven by a puberty-linked surge in androgens<\/strong> acting on the sebaceous glands of a face whose oil chemistry and follicular biology are still stabilising. It usually responds well to standard topical and oral therapy and, in most cases, eventually resolves on its own. Adult-onset acne \u2014 defined broadly as acne that either persists past the mid-twenties or appears for the first time in adulthood \u2014 behaves differently.<\/p>\n

The distribution is different (jawline, chin, lower cheeks and neck rather than the T-zone), the timing is often cyclical, and the response to teenage-style therapy is often disappointing.<\/p>\n

Four systemic drivers explain most of what we see in the adult acne clinic:<\/p>\n

Androgen shift and hormonal cycling<\/h3>\n

Even in women without a formal diagnosis of polycystic ovary syndrome (PCOS), the ratio of androgens to oestrogens shifts across the menstrual cycle and again in perimenopause. Free testosterone drives sebum production. Follicular hyperkeratinisation follows.<\/p>\n

The cystic, deep, tender lesion along the jawline seven days before menstruation is the clinical signature. PCOS itself \u2014 a condition considerably under-diagnosed in the Japanese adult population \u2014 deserves specific consideration in any woman with adult acne, particularly when acne coexists with irregular cycles, hirsutism, weight gain or insulin resistance. Recent 2024 evidence continues to confirm the strong link between PCOS-driven hyperandrogenism and treatment-resistant adult acne.[1]<\/sup><\/p>\n

Insulin and IGF-1<\/h3>\n

A high-glycaemic diet \u2014 one built around refined carbohydrates, sweetened drinks and starchy convenience foods \u2014 raises circulating insulin. Insulin raises insulin-like growth factor 1 (IGF-1)<\/strong>. IGF-1 acts directly on the sebaceous gland, increasing sebum output and follicular hyperkeratinisation, and it also amplifies androgen receptor signalling. The clinical consequence is more lesions, larger lesions, and slower healing. A 2024 randomised controlled trial and a 2025 meta-analysis both reported that a low-glycaemic-load diet significantly reduces both lesion count and IGF-1 in adults with moderate acne over twelve weeks.[2]<\/sup><\/p>\n

Dairy \u2014 particularly skim dairy<\/h3>\n

The dairy-acne relationship has moved from controversial to reasonably well-established. Multiple cohort studies and, more recently, a 2024 systematic review point to a modest but consistent association between dairy intake and adult acne severity, with skim and low-fat dairy showing a stronger effect than full-fat.[3]<\/sup> The proposed mechanism combines the IGF-1-elevating effect of milk proteins (particularly whey) with the residual bovine hormones present in commercial dairy. In our clinic we do not blanket-eliminate dairy for every acne patient, but we routinely trial a four-week dairy withdrawal in patients whose acne has resisted standard care, and roughly half report meaningful improvement.<\/p>\n

Gut dysbiosis and the gut-skin axis<\/h3>\n

The concept of a gut-skin axis is no longer speculative. Contemporary reviews consistently document that patients with adult acne show shifts in gut microbial composition compared with matched controls \u2014 reduced microbial diversity, lower abundance of short-chain-fatty-acid-producing species, and altered ratios of Bacteroidetes to Firmicutes.[4]<\/sup> The mechanisms proposed include increased intestinal permeability, systemic low-grade inflammation, and altered bile acid metabolism affecting skin lipid biology. Practical implication: adult acne that has resisted standard care warrants a look at gut function even when there are no overt gut symptoms.<\/p>\n

Rosacea and the SIBO connection<\/h2>\n
\"adult<\/figure>\n

Rosacea<\/strong> has followed a similar arc from “skin condition of unknown origin” to “systemic condition with a strong gut signature”. The single most important observation of the past fifteen years in rosacea research is the association with small intestinal bacterial overgrowth (SIBO)<\/strong>.<\/p>\n

A landmark 2008 Italian study reported SIBO prevalence of 46 percent in patients with rosacea versus 5 percent in controls, and \u2014 critically \u2014 that eradication of SIBO with rifaximin produced complete or near-complete clearance of rosacea lesions in the majority of treated patients, with sustained remission at nine months.[5]<\/sup><\/p>\n

That finding has been replicated with variations across subsequent cohorts. A 2024 review of the gut-skin axis in rosacea reinforced the SIBO link and added Helicobacter pylori<\/em>, altered small-bowel motility and gut barrier dysfunction to the shortlist of gut-based contributors.[6]<\/sup><\/p>\n

The clinical translation is straightforward. A patient with rosacea \u2014 particularly the papulopustular subtype \u2014 who also has any of the classic SIBO symptoms (post-meal bloating, unexplained flatulence, alternating stool habit, food sensitivities) should have SIBO on the differential. Treating the SIBO frequently produces the skin improvement that topical therapy alone was unable to deliver.<\/p>\n

For a fuller treatment of SIBO \u2014 diagnosis, breath testing, the 4R protocol and product selection \u2014 see our companion article on SIBO and gut health in Tokyo<\/a>.<\/p>\n

The dietary and lifestyle triggers we ask patients to eliminate<\/h2>\n
\"adult<\/figure>\n

The Remove phase for skin follows the same logic as the Remove phase for gut work. Before adding anything, we take away the inputs that are known to worsen the biology we are trying to fix. The two conditions have overlapping but not identical trigger lists.<\/p>\n

Triggers to eliminate for adult acne<\/h3>\n