Inflammatory skin — acne, rosacea, eczema, psoriasis

What actually decides this outcome, in order of size

The single largest determinant here is not on the list of fourteen options: it is which of the four diseases you actually have. They share a page because they share a look, and they share almost no cytokine biology.

1. The diagnosis. Plaque psoriasis is an IL-23 to IL-17 axis disease of the keratinocyte. Atopic dermatitis is IL-4 and IL-13 signaling through JAK-STAT with a filaggrin barrier defect underneath it. Rosacea runs on cathelicidin LL-37 processed by an overactive kallikrein-5 protease. Acne needs sebum, follicular hyperkeratinization and Cutibacterium acnes together. A zinc capsule cannot be right for all four.
2. Severity, because it decides the whole category of treatment. The Cochrane network meta-analysis of chronic plaque psoriasis compares systemic drugs against each other because that is the comparison that exists at moderate to severe disease Sbidian 2022. In atopic dermatitis, dupilumab reached the primary endpoint in 38% and 37% of patients across two arms against 10% on placebo in 671 and 708 patients (P<0.001) Simpson 2016. Those are the effect sizes a supplement is being compared with, and it is not close.
3. The barrier, which is the half you can actually influence. Ceramide and free fatty acid content of the stratum corneum sets transepidermal water loss, and in atopic skin it is measurably low. This is where a topical earns more than a capsule.
4. Androgens and glycemic load, for acne only. 5-alpha-reductase in the sebaceous gland converts testosterone to DHT locally, and insulin and IGF-1 raise sebum output. This is why an acne that started at 25 in a woman with irregular cycles is an endocrine finding rather than a skincare one.
5. The supplement shelf, fifth. Zinc, omega-3 and vitamin D have real mechanisms here. In 25,871 adults, 2000 IU/day of vitamin D did not change hard outcomes Manson 2019, which is the right prior for how large a nutrient effect on skin is likely to be.

The order to run these in, and what has to be true first

Name the disease, gate on severity, fix the barrier, and only then test and supplement. The fourteen options on this page all belong at step four.

1. Name it. Silvery plaques on extensors with nail pitting is not the same disease as flexural lichenified itch, and neither is centrofacial flushing with telangiectasia. The wrong name makes every subsequent step wrong.
2. Gate on severity. More than about 10% body surface area, or any involvement of face, hands or genitals, is a prescription conversation and not a shelf one Sbidian 2022.
3. Barrier and topicals first. Tretinoin normalizes follicular keratinization over a full 28-day epidermal turnover cycle, and Fluocinolone is the short-course topical steroid for an inflammatory flare. Both act where the disease is.
4. Test, if the acne is hormonal or the picture is systemic. Total Testosterone with Free Testosterone and SHBG (Sex Hormone-Binding Globulin), DHEA-S for the adrenal fraction, and 17-OH Progesterone before 9am in the follicular phase for non-classical congenital adrenal hyperplasia. Add Fasting Insulin with HbA1c (Hemoglobin A1c) where the pattern is jawline acne with irregular cycles, and hs-CRP (High-Sensitivity C-Reactive Protein) where the skin disease is extensive.
5. Then the internal options, matched to the finding. Zinc where Zinc, Plasma is low and the disease is acne, Omega-3 (Fish Oil) for the resolvin and protectin arm of inflammation resolution, Vitamin D where 25(OH)D is low, DIM where the estrogen ratio is the argument, NAC for the excoriation habit, Probiotic and Gut Repair (EnteroMend) where a gut complaint runs alongside the skin one, and KPV as the melanocortin fragment with the most specific anti-inflammatory rationale on the list.

What gets bought for this that cannot move it

Nothing on this page clears moderate to severe psoriasis. The Cochrane review of systemic treatments exists because the honest comparison at that severity is between biologics, not between a biologic and a capsule Sbidian 2022. A reader with 20% body surface involvement who buys this pathway is delaying the treatment that works, and psoriatic arthritis develops in a substantial minority while they wait.

Nor moderate to severe atopic dermatitis. A 38% versus 10% primary endpoint in 1,379 randomized patients is what an IL-4 receptor blockade produces Simpson 2016. Evening primrose oil has been tested for eczema repeatedly and is not that.

Acne that scars needs isotretinoin, and even isotretinoin is not permanent. Of 405 patients followed after a course, 94 (23.2%) relapsed severely enough to seek further treatment, and 76 of those 94 (80.9%) did so within 2 years Liu 2008. That is the ceiling on the strongest drug in the class, which is the right context for judging anything weaker.

And if the skin is a symptom of something else, this is the wrong pathway. A malar rash with joint pain and fatigue is a question for ANA (Antinuclear Antibodies) and ESR (Sed Rate), not for a barrier cream. Sudden widespread itch without a rash is a hepatobiliary and hematologic question. Neither is on this page.

How you would know it was working, on a real read-out and a real timescale

Skin is the one goal where the read-out is partly photographic, and the timescale is set by keratinocyte biology rather than by patience.

• Photographs in fixed lighting at 0, 6 and 12 weeks. The epidermis turns over in about 28 days, so no topical acting on keratinization can be judged before two full cycles. Acne reliably worsens in weeks 2 to 4 of a retinoid before it improves, and that purge is the commonest reason a working treatment gets abandoned.
• hs-CRP (High-Sensitivity C-Reactive Protein) at 12 weeks where the disease is extensive. Psoriasis carries measurable systemic inflammation, and interleukin-6 driven hepatic CRP is the cheapest index of it. A fall of more than 1 mg/L alongside visible clearing is a real signal.
• Zinc, Plasma at 12 weeks if you supplemented zinc. Plasma zinc falls during the acute-phase response, so an inflamed skin disease depresses the very marker you are using to justify the capsule.
• Free Testosterone and SHBG (Sex Hormone-Binding Globulin) at 12 weeks for hormonal acne. Sebum output tracks androgen exposure with a lag of about 6 to 8 weeks, so the lesion count moves a full cycle after the hormone does.
• Vitamin D (25-Hydroxy) at 8 to 12 weeks. Four to five half-lives of 2 to 3 weeks each.

What will fool you. Every inflammatory skin disease remits and relapses on its own, so a 4-week improvement is as likely to be the disease as the treatment. Sun exposure improves psoriasis and worsens rosacea, which means a summer trial and a winter trial answer different questions. And a topical steroid started in the same fortnight as a supplement makes the supplement look like it worked.

Sources read for these sections

• Sbidian E. Systemic pharmacological treatments for chronic plaque psoriasis: a network meta-analysis. Cochrane Database of Systematic Reviews 2022;5(5):CD011535 · PMID 35603936
• Simpson EL. Two Phase 3 Trials of Dupilumab versus Placebo in Atopic Dermatitis. New England Journal of Medicine 2016;375(24):2335-2348 · PMID 27690741
• Liu A. Relapse of acne following isotretinoin treatment: a retrospective study of 405 patients. Journal of Drugs in Dermatology 2008;7(10):963-6 · PMID 19112761
• Manson JE, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. The New England Journal of Medicine, 2019 · PMID 30415629