The Skin-Fold Rash After Fast Weight Loss

The fast answer

A red, raw, sometimes weeping patch where skin sits against skin has a name: intertrigo. Under the breasts, in the crease of the abdomen, in the groin. It stings in the shower, it is worse in summer, and almost nobody mentions it out loud.

Three things to know before you decide the medication caused it:

• It is probably not where you think. In the largest recent series, the commonest site by a wide margin was under the breast — the groin was the least common of the three reported².
• Losing weight is on the list of things that fix this, not the list that causes it. The dermatology review of skin after weight-loss surgery puts intertrigo among the conditions that improve or resolve¹.
• Keeping the fold dry beat treating it. In the one randomized comparison anyone has run, a moisture-wicking fabric nearly halved the time to resolution².

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Where it actually shows up

The useful numbers come from a 2025 study of 2,778 inpatients with obesity (mean age 63.9, mean BMI 43.4). Intertrigo was found in 15.9% of them².

Of the sites the researchers reported, the distribution was not the one most women expect:

Those three do not add to 100% because they are the reported sites, not the complete list. But the ranking is the point. If you have been quietly worrying about the groin, the fold most likely to actually give you trouble is the one under your bra.

The study also found it more common with higher BMI, in women, and in patients over 65² — which is the first hint that the direction of travel is not what the internet assumes.

The direction is the opposite of what you would guess

Here is the finding worth the whole page.

A 2026 narrative review looked at what happens to skin across bariatric surgery, and it splits its findings into two lists. Intertrigo sits on the list of conditions that surgery improves or resolves, alongside acanthosis nigricans, hidradenitis suppurativa, psoriasis, skin tags and hirsutism¹.

The list of conditions that weight-loss surgery may precipitate or exacerbate is a different one: xeroderma — dry skin — plus panniculitis, purpura, vasculitis and alopecia¹.

So the honest read is this. Less fold means less skin-on-skin, less trapped sweat, and less of the warm damp environment intertrigo needs. On the current evidence, weight loss is the treatment for this rash, not the trigger. If something on your skin genuinely got worse as the weight came off, dryness and hair thinning are the better-supported complaints — and hair has its own protocol here.

The honest limit: that review is about bariatric surgery, not about GLP-1 medications. More on that below.

When it is in the groin, itch does not mean yeast

This is the actionable half.

A cross-sectional study followed 70 women presenting with vulval itch to a dermatology clinic. Infections explained 69% of cases, and vulvovaginal candidiasis was the single commonest cause at 27.1%³.

Which means 31% were not an infection at all — conditions like lichen simplex chronicus and lichen sclerosus³.

Read that limitation before you use the number: 70 women, at one tertiary dermatology clinic, all of whom had already been referred for a persistent symptom. That is not the general population, and it is certainly not a GLP-1 population. What it is good for is the shape of the answer, not the exact share.

And the shape of the answer is worth an appointment: if two weeks of antifungal cream has not touched it, the answer is not more antifungal cream. Lichen sclerosus in particular needs a different treatment entirely, and it is not something to keep managing privately out of embarrassment.

What resolved it fastest

Inside that 2,778-patient study sat a genuine randomized comparison. 40 patients with intertrigo were split between a moisture-wicking, silver-infused fabric placed in the fold and traditional treatment.

The fabric group's symptoms resolved in 6.0 days on average, against 11.0 days for standard care — a difference the authors report as statistically significant². The authors declare no conflicts of interest.

Forty patients is a small trial, in older inpatients with severe obesity, and the product tested is a specific commercial fabric rather than a category. Do not read it as proof that one brand works. Read it as the mechanism: the thing that shifted the outcome was keeping the fold dry, not what was applied to it. A soft absorbent barrier changed daily, and a fold dried properly after a shower, are the cheap version of the same idea.

What nobody has studied

None of this is a GLP-1 cohort. The prevalence work is in obesity, the improve-or-resolve list is post-surgical, and the vulval-itch series is a dermatology clinic.

Nobody has looked at skin folds in people losing weight on semaglutide or tirzepatide, and there is one reason to think the answer might not transfer cleanly: weight lost quickly can leave redundant skin, and redundant skin can form a fold where there was not one before. That is a reasonable inference from how the rash works. It is not a finding, nobody has measured it, and it is written here as the open question it is.

When to stop self-treating

Take it to a clinician if the fold is persistently sore, weeping, bleeding, or has a smell. Those are signs of infection or a diagnosis that is not intertrigo — both treatable, and neither improved by waiting.

For a 12-minute appointment, the sentence that does the most work is the location and the timeline: "It is under my left breast, it has been six weeks, and two weeks of clotrimazole did nothing." That tells a clinician to stop assuming yeast, which is exactly the assumption that costs women months here.