Acne

Acne is follicular inflammation with sebum, bacteria, and keratin plugging. Mainstream care uses topical antiseptics, antibiotics, and hormones. In Peat's nutritional and hormonal skin-metabolism frame, Thyroid hormone speeds the conversion of cholesterol into youth-related steroids, which can bring on acne and raises the need for Vitamin A. A shortage of vitamin A weakens immunity and lets bacteria grow in the skin.

In *Rosacea, inflammation, and aging*, Peat grouped acne rosacea with the same mitochondrial inefficiency, excess blood flow, and lactic-acid themes as kidney and diabetic fibrosis, arguing surface skin changes mirror deeper degenerative processes.

Diet and hormones

Vitamin A affects the differentiation of skin cells, the production of steroids, and resistance to infection and inflammation. The great increase in formation of the sex steroids at puberty increases the need for vitamin A, and makes its regulatory actions more important. Thyroid's important functions for the skin are the production of steroids and preventing their imbalance, and maintaining the immune function and production of sebum.

— Ray Peat

The balance between vitamin E and unsaturated fats affects how vitamin A and thyroid work, so Peat named liver, Eggs, oysters, fruits, and Milk as Foods to include. Estrogen from contraceptives clears acne in many women by shrinking the oil glands, so the skin supports less bacterial growth.

Early high-estrogen oral contraceptives increased acne rosacea more than threefold in studies Peat cited on the rosacea page. Sensitivity to light can rise when porphyrin precursors accumulate; alcohol is often blamed without justification.

Topical treatments

Ten percent sulfur soap leaves an antiseptic skin residue that can prevent infection, and Peat put it first among acne treatments to try. He used plain sulfur soaps and had not tried ones with salicylic acid. A similar sulfur-based formulation, 10% sodium sulfacetamide/5% sulfur emollient foam, produced clinically significant improvement in an open-label case series of 8 rosacea patients. Sulfur lingers on the skin for at least a day and can leave a smell. Flowers of Sulfur taken internally can help, but with long use the intestine can grow sensitive to the sulfur and become irritated.

Aspirin dissolved in water and put on the skin eases inflammation and is mildly germicidal. Topical Caffeine is antiseptic and anti-inflammatory as well. Precipitated or sublimed sulfur can be mixed with water into a slurry and patted onto the area, and dissolved aspirin added to it strengthens the antiseptic effect. Benzoyl peroxide may age the skin, and Peat offered topical sulfur with oral tetracycline instead.

The excitatory metabolite glutamate, and nitric oxide, are both inhibited by aspirin.

— Ray Peat

Tetracycline antibiotics are usually taken by mouth for acne because of their anti-inflammatory effect, and changing the diet during a course can make the benefit permanent. In a randomized placebo-controlled trial, doxycycline at a dose too low to kill bacteria reduced acne lesions over 6 months. Skin bacterial counts did not differ from placebo. For a topical antibiotic, an over-the-counter neomycin lotion is the easiest choice. Peat advised against antibiotics during Pregnancy.

On human skin, one dose of 10% benzoyl peroxide wiped out most of the vitamin E in the outer layer; a vitamin E lotion limited the lipid damage but not the water loss.

Supplements and metabolic context

Both Vitamin A and Zinc are essential for healthy skin in the right amount, but too much of either can disturb immunity. Some products sold as Vitamin E now contain significant PUFA. The right amount of Thyroid is essential for skin immunity and for steroid metabolism in the skin.

Rosacea-prone skin can show three to four times normal blood flow with impaired oxygen extraction in measurements Peat cited, suggesting mitochondrial defects as a shared driver with acne variants. Riboflavin, thiamine, and faster intestinal transit to lower Endotoxin appear in his rosacea nutrition themes and overlap acne care. See Harm reduction.

In a randomized double-blind trial of 80 patients with moderate acne, adding an oral probiotic to standard doxycycline treatment produced significantly better lesion improvement than doxycycline alone over 3 months. Gut health may shape acne severity alongside direct antibacterial action.

In a 12-week double-blind trial of 36 patients aged 18 to 30, fermented milk with 200 mg of lactoferrin daily (18 patients) cut inflammatory lesion count by 38.6%, total lesion count by 23.1%, acne grade by 20.3% and sebum content by 31.1% compared with fermented milk alone (18 patients).

Low vitamin D tracked inflammatory acne in a Korean case-control study: 48.8% of 80 acne patients were deficient (25(OH)D below 12 ng/mL) versus 22.5% of 80 healthy controls, and lower 25(OH)D correlated with more inflammatory lesions (r = −0.512). In the randomized placebo-controlled follow-up of 39 deficient patients, oral cholecalciferol 1000 IU/day for 8 weeks cut inflammatory lesions by 34.6% versus 5.8% on placebo, with no difference in non-inflammatory or total lesion counts.

In ten healthy people, vitamin B12 supplements switched off the skin bacterium's own B12-making genes, and in culture extra B12 made the same bacterium produce more porphyrins; one of the ten developed acne within a week. In a skin-cell model, porphyrins from acne-linked strains made keratinocytes leak potassium, which switched on the NLRP3 inflammasome and IL-1β release.

Dairy, thyroid, and pimples

Acne that appears with dairy can come from the rise in metabolic rate that calcium causes, which uses up vitamin A, usually the limiting nutrient. Topical progesterone can make a pimple regress almost at once, though acne usually involves a bacterial infection and a poor immune reaction, and vitamin A and thyroid function are needed for skin cells to differentiate.

Because thyroid hormone speeds the conversion of cholesterol to progesterone and DHEA, the resulting surge of youth-associated hormones can bring teenage-style acne even to a 50-year-old; too much protein relative to carbohydrate can also lower blood sugar and trigger a cortisol stress reaction.

Gut microbiota

Patients with acne vulgaris have lower fecal Shannon diversity than matched controls, with less Firmicutes and more Bacteroidetes-group taxa; Clostridia, Lachnospiraceae, and Ruminococcaceae taxa often treated as beneficial were depleted. In a separate moderate-to-severe acne cohort, Actinobacteria and genera including Bifidobacterium and Lactobacillus were lower while Proteobacteria were higher than in healthy controls.

In a small laboratory study, blood from people with deep inflammatory acne formed tiny clots when bacterial endotoxin was added, which rarely happened with mild acne and never with healthy controls. Half of the most severe cases formed clots even without added endotoxin.

In a small randomized, double-blind, placebo-controlled pilot trial in adults with acne, 12 weeks of oral Lactobacillus rhamnosus SP1 normalized skin insulin-signaling genes (lower IGF1, higher FOXO1; no change on placebo) and made physician-rated improvement far more likely.

Rosacea

Rosacea is chronic facial erythema with telangiectasia, flushing, and sometimes rhinophyma or ocular involvement, with at least 10% prevalence reported among white adults. Dermatology often treats it symptomatically with lasers, antibiotics, or chronic tetracycline for anti-inflammatory effect.

In *Rosacea, inflammation, and aging: The inefficiency of stress*, rosacea is surface-visible mitochondrial inefficiency: excess blood flow with poor oxygen use, lactic acid, neovascularization, and fibrosis shared with kidney, diabetic, and cancer pathology.

Rosacea is a physiological problem that deserves consideration in the light of all that's known about physiology and developmental biology.

— Ray Peat

Mitochondria, light, and lactic acid

Rosacea-prone skin can show three to four times normal blood flow with impaired oxygen extraction in cited measurements. Warburg-type aerobic glycolysis, mitochondrial riboflavin destruction by blue and UV light, and lactic acid as a "phlogogen" tie flushing to energy failure.

Riboflavin, vitamin B2, is an essential component of the mitochondrial respiratory enzymes, and it is very easily destroyed by light (blue light and especially ultraviolet).

— Ray Peat

When mitochondria are damaged, active cells produce increased amounts of lactic acid, even in the presence of adequate oxygen. Otto Warburg identified this kind of metabolism, aerobic glycolysis, as an essential feature of cancer, and showed that it could be produced by stress, ionizing radiation, carcinogenic toxins, and even by a simple oxygen deficiency.

Vitamin K protects mitochondrial complex I with coenzyme Q; PUFA breakdown products inhibit respiration and amplify glutamate excitation. Aspirin inhibits pathways overlapping nitric oxide and glutamate.

Estrogen and vascular overgrowth

Incidence rises after age 30 in sun-exposed areas; the timing tracks declining Progesterone with tissue estrogen effects, not sun alone. Estrogen promotes lactic acid, porphyrin precursors, nitric oxide, and fibroblast collagen synthesis. Early high-estrogen oral contraceptives increased acne rosacea more than threefold in cited studies.

Localized stress first produces vasodilation to deliver more blood; hypoxia prolonged enough tends toward neovascularization and fibrosis. Corneal neovascularization (pannus) can seriously impair vision when invasive vessel growth is unchecked.

SIBO and gut endotoxin

SIBO prevalence was higher in rosacea patients than sex- and age-matched controls (52/113 vs 3/60). After rifaximin eradication of SIBO, cutaneous lesions cleared in 20 of 28 and greatly improved in 6 of 28, versus placebo patients who stayed unchanged or worsened; switched placebo cases later cleared as SIBO cleared, and benefit held for at least 9 months.

Reducing gut transit time below about 30 hours remitted rosacea in a patient without digestive-tract disease. Intestinal Endotoxin (bacterial lipopolysaccharide) is a candidate driver of that gut-skin link; faster transit lowers the toxin load reaching general circulation.

A nationwide Danish cohort of 49,475 rosacea patients versus 4,312,213 general-population controls found higher rates of coeliac disease, Crohn disease, ulcerative colitis, and irritable bowel syndrome. Register-coded Helicobacter pylori infection and SIBO were not associated in that analysis.

Mainstream treatment and prevention

Lasers, chemical abrasion, and chronic tetracycline target symptoms while physiology regulating vessel and fibroblast growth is ignored elsewhere in medicine. Tetracycline helped when rosacea was thought infectious because some antibiotics have anti-inflammatory actions apart from germicide.

Riboflavin, thiamine, Selenium, niacinamide, Caffeine (when energy efficiency, not hot-fluid flushing, is the issue), and faster intestinal transit to lower Endotoxin are relevant themes. Case reports include riboflavin relieving nosebleeds and facial flushing tied to mitochondrial deficit. See Acne, Light, Harm reduction.

Skin

Skin is the outer organ: barrier, sensory surface, vitamin D factory, and display of internal energy. Dryness, inflammation, slow healing, and gray tone track low thyroid, low vitamin A, copper-iron imbalance, and PUFA oxidation.

Internal mirrors

Progesterone and thyroid improve skin quality in the primary literature. Excess cortisol thins skin. Free unsaturated fats and iron feed age pigment and damage. See Thyroid, Progesterone, Cortisol, Vitamin A, Copper, Iron, PUFA.

Light both makes vitamin D and, in excess UV, damages; red light supports respiratory enzymes in deeper tissue. See Light, Red light, Vitamin D3.

Light on the skin may raise local steroid production without other organs; orange and red frequencies appear especially important.

I suspect that light on the skin directly increases the skin's production of steroids, without depending on other organs. Different steroids probably involve different frequencies of light, but orange and red light seem to be important frequencies.

— Ray Peat

Gut microbial composition and oral probiotic trials associate with several inflammatory skin diseases (rosacea / SIBO, atopic eczema, psoriasis, acne); see Gut#Gut-skin axis. A 2021 narrative review frames that gut-skin axis without adding primary trial data of its own.

One thing to consider when you have both bowel and skin symptoms is that the bowel is actually causing or contributing to the skin problem. And eliminating gluten, for example, sometimes clears up both the bowel and skin problem because some of the same enzymes are activated by inflammation that cause the premature hardening and flakiness of the skin.

— Ray Peat

Practice

Heal from inside: food, thyroid, minerals, lower seed oils. Topical steroids are short tools with rebound risk. See Topical steroid withdrawal, Harm reduction.

Burns

Burns destroy the skin barrier through heat, chemical, or electrical injury. Severity is judged by depth (first through third degree) and the percentage of body surface involved. Cool a minor burn under running water for 10-20 minutes; do not use ice, which can worsen tissue damage. Cover loosely, avoid butter or oils on the wound, and seek emergency care for large, deep, or facial/genital burns, or any burn on a child or older adult. Direct Peat commentary on burn first aid specifically is not established in the corpus searched for this page; his broader framework on wound healing (adequate protein, vitamin A, and hormonal balance) applies to recovery once the acute injury is stabilized.

UV nail dryers and cell damage

UV-emitting nail polish dryers used for gel manicures cause DNA damage, cell death, and cancer-associated mutations in exposed skin cells, the same category of damage as other UV sources. Across mouse and human cell lines, a single 20-minute irradiation killed 20-30% of cells, and three consecutive 20-minute sessions killed 65-70%.