Quick answer: Functional dermatology recognizes that skin conditions — from androgenic alopecia to psoriasis, acne, and premature aging — are not isolated skin diseases but visible manifestations of internal physiological dysfunction: insulin resistance, gut dysbiosis, sex hormone imbalance, chronic inflammation, nutrient deficiencies, and mitochondrial stress all express themselves through the skin, and addressing these upstream drivers produces skin improvements that no topical treatment alone can match.

The skin is the body’s largest organ and its most visible systemic readout — what’s happening in the gut, liver, hormonal system, and immune network is literally written on the face and scalp. Conventional dermatology treats skin conditions topically and symptomatically — topical retinoids, antibiotics, immunosuppressants, biologics — without interrogating why the skin became inflamed, hyperpigmented, thinned, or seborrheic in the first place. Functional dermatology asks: what upstream biological dysfunction is manifesting in this organ? This guide examines functional medicine’s evidence-based approach to four of the highest-burden skin conditions: androgenic alopecia (hair loss), psoriasis, acne vulgaris, and skin aging.

Androgenic Alopecia: Beyond DHT — The Metabolic Root Causes of Hair Loss

Androgenic alopecia (AGA) — pattern baldness affecting 50% of men by age 50 and 40% of women by age 70 — is conventionally explained entirely by DHT (dihydrotestosterone) binding to 5-alpha-reductase-converted follicle androgen receptors, causing miniaturization. This is accurate but incomplete: DHT explains the genetic susceptibility and follicular susceptibility pattern, but does not explain why metabolic health strongly modifies AGA severity. Follicle miniaturization involves: DHT-mediated follicle androgen receptor activation → TGF-β1 upregulation → keratinocyte apoptosis → shortened anagen phase → vellus conversion. Simultaneously: chronic scalp inflammation (microinflammation around follicles), subcutaneous scalp fibrosis (perifollicular), and microvascular insufficiency (reduced scalp blood flow) contribute to miniaturization progression independent of DHT.

Insulin resistance — through IGF-1/IGFR-mediated androgen signaling — significantly amplifies AGA. Elevated insulin stimulates ovarian and adrenal androgen production in women; systemic IGF-1 amplifies androgen receptor sensitivity in follicles. Matilainen et al. (2000, Journal of the American Academy of Dermatology) found men with premature AGA (onset <35 years) had significantly higher fasting insulin and insulin resistance than age-matched controls without AGA. Thyroid dysfunction — both hypothyroidism and hyperthyroidism — produces hair shedding (telogen effluvium) that is frequently misdiagnosed as or complicates AGA. Iron deficiency — even without frank anemia, ferritin below 40–70 ng/mL impairs follicle cycling; Trost et al. (2006, Journal of the American Academy of Dermatology) documented significant AGA correlation with low ferritin in women. Zinc deficiency similarly impairs hair follicle proliferation (zinc is rate-limiting for follicle matrix cells); Kil et al. (2013, Annals of Dermatology) found serum zinc inversely correlated with female pattern hair loss severity.

Functional medicine AGA approach: (1) Metabolic workup — fasting insulin, HOMA-IR, comprehensive thyroid (TSH, free T3/T4, reverse T3, thyroid antibodies), ferritin (target 70–100 ng/mL for hair), zinc RBC, vitamin D; (2) Hormonal workup in women — DHEA-S, free and total testosterone, 17-OHP (rule out CAH), SHBG, prolactin, LH/FSH; (3) Scalp microbiome — Malassezia species colonization drives seborrheic dermatitis that exacerbates AGA through scalp inflammation; zinc pyrithione and ketoconazole targeting Malassezia reduce this inflammatory component; (4) Nutritional optimization — iron/ferritin repletion (often requires 6+ months), zinc 25–45mg, biotin 2,500–5,000μg (required for follicle keratinization, though deficiency is rare in adults), marine collagen hydrolysates (Maia Campos 2015 RCT — 2g marine collagen daily for 90 days significantly improved hair density); (5) Scalp blood flow — microneedling (1.5mm dermaroller) weekly creates growth factor release (VEGF, PDGF) and disrupts perifollicular fibrosis — Dhurat 2013 RCT showed 30% additional hair density improvement vs minoxidil alone; low-level laser/red light therapy (LLLT) — 25+ RCTs support photobiomodulation for AGA; LLLT devices (HairMax, Theradome) are FDA-cleared.

Psoriasis: The Gut-Skin Axis and Systemic Inflammation

Psoriasis — a chronic immune-mediated skin condition affecting 2–3% of the Western population — is definitively a systemic inflammatory disease, not just a skin disease. The IL-23/Th17 axis is the central pathogenic driver: IL-23 from dendritic cells stimulates Th17 cells to produce IL-17A, IL-17F, IL-22, and TNF-α — cytokines that drive keratinocyte proliferation (6× normal turnover), neutrophil recruitment, and epidermal barrier disruption. Psoriasis patients carry 2–3× higher cardiovascular risk (Mehta 2010, JAMA), 4-6× higher metabolic syndrome prevalence, elevated depression rates, and significantly higher rates of psoriatic arthritis (30%), IBD, uveitis, and other immune-mediated conditions — reflecting the systemic immune dysregulation underlying what appears to be a skin disease.

The gut-psoriasis connection is well-established. Leaky gut (increased intestinal permeability) allows LPS and bacterial antigens to reach systemic circulation, fueling the IL-23/Th17 cascade. Psoriasis patients have measurably different gut microbiomes: reduced Akkermansia, Faecalibacterium prausnitzii, and Bacteroidetes with enrichment of Firmicutes — the same dysbiosis pattern seen in IBD. Scher et al. (2015, Journal of Investigative Dermatology) documented specific microbiome signatures in psoriatic arthritis patients — evidence that gut microbial changes precede or accompany joint involvement. Gluten sensitivity and psoriasis have documented association: Michaëlsson et al. (2000) found 16% of psoriasis patients have celiac-level anti-gliadin antibodies, and gluten-free diet produced significant skin improvement in those patients.

Functional medicine psoriasis interventions with evidence: Omega-3 fatty acids — Mayser 1998 RCT (n=83) found IV fish oil reduced PASI (psoriasis severity) 11.2 vs 7.5 in placebo; oral omega-3 meta-analysis (Millsop 2014) supports moderate benefit, mechanism through competitive EPA/DHA incorporation reducing pro-inflammatory arachidonic acid metabolites; dose: 3–4g EPA+DHA daily. Vitamin D — Topical vitamin D analogs (calcipotriol) are first-line conventional therapy; systemic vitamin D3 optimization to 60–80 ng/mL reduces psoriasis severity through Th17 suppression and Treg promotion. Low-calorie, Mediterranean, or low-inflammatory diet — Naldi 2014 (n=3,557) found Mediterranean diet adherence inversely correlated with psoriasis severity; Phan 2012 meta-analysis confirmed dietary interventions reduce PASI. Curcumin — Kurd 2008 open-label study 4.5g/day curcumin showed significant PASI improvement; mechanism through NF-κB and Th17 pathway inhibition. Gut restoration — probiotics, particularly Lactobacillus reuteri and Bifidobacterium species, reduce intestinal permeability and modulate IL-23/Th17 axis.

Acne Vulgaris: Insulin, IGF-1, and the Western Diet Connection

Acne vulgaris — affecting 85% of adolescents and an increasing proportion of adults — was once attributed purely to Cutibacterium acnes (formerly Propionibacterium acnes) and sebum production. The modern functional medicine understanding is more nuanced: acne is fundamentally driven by IGF-1/insulin-mediated sebaceous gland activation. Melnik (2012, Acta Dermato-Venereologica) synthesized the evidence for the “acne-insulin-IGF-1-mTORC1 axis” — the pathway connecting Western diet → hyperinsulinemia → IGF-1 elevation → FoxO1 suppression → mTORC1 activation → androgen receptor upregulation + sebocyte lipogenesis + follicular hyperkeratinization → acne. This model explains why population studies find essentially zero acne in non-Westernized populations (Lindeberg 2003 Kitava study; Cordain 2002 examining Aché hunter-gatherers and Kitavan Islanders — zero acne in 1,200 individuals examined) — populations with low-glycemic, low-dairy, low-processed-food diets.

Dairy’s relationship with acne is particularly evidence-supported: Adebamowo 2005–2006 (three large Harvard Nurses’ Health Study cohort studies, combined n=47,355) found positive association between dairy consumption — particularly skim milk — and acne, with skim milk showing stronger association than whole milk (whey protein and IGF-1 in milk, not fat, are the acne drivers). Insulin/glycemic index: Kwon 2012 RCT (n=32) found low-glycemic-load diet for 10 weeks reduced acne lesion count 65.7% versus 28% high-GI control — a dramatic and clinically meaningful reduction. Smith 2007 RCT (n=43, 12 weeks low-GI vs high-GI) confirmed reduced inflammatory lesions and improved insulin sensitivity with low-GI diet.

Functional medicine acne protocol: (1) Low-glycemic, dairy-free diet for 12-week trial — the highest-yield dietary intervention; (2) Zinc supplementation — zinc reduces 5-alpha-reductase activity (lowering DHT-driven sebum production), inhibits C. acnes, and reduces IL-6; Verma 1994 meta-analysis confirmed zinc as effective as oral tetracycline in mild-moderate acne; dose: zinc gluconate 30mg or zinc acetate 30mg; (3) Vitamin A — retinoic acid is the active form that reduces follicular hyperkeratinization (the same mechanism as isotretinoin); beta-carotene and retinol from diet support this pathway; (4) Nicotinamide (niacinamide) 4% topical has equivalent efficacy to clindamycin gel in multiple RCTs with no antibiotic resistance concerns; oral niacinamide 750mg reduces sebum production; (5) Gut-skin axis — eliminating SIBO, reducing dysbiosis (particularly Blastocystis and pathobionts), and L. rhamnosus GG supplementation (Bowe 2014 — reduced IGF-1, improved acne) address the gut-driven systemic IGF-1 pathway.

Skin Aging: Collagen, Glycation, and Mitochondrial Photoaging

Skin aging is driven by two processes: intrinsic aging (chronological — telomere shortening, mitochondrial ROS accumulation, declining fibroblast activity, reduced collagen synthesis) and extrinsic aging (photoaging from UV radiation — approximately 80% of visible facial aging). UVA penetrates deeply into the dermis, generates ROS that damage collagen and elastin directly, and activates matrix metalloproteinases (MMPs) that degrade existing structural proteins. UV also promotes glycation — the non-enzymatic cross-linking of proteins by sugar — creating advanced glycation endproducts (AGEs) that stiffen collagen, reduce elasticity, and cause characteristic yellowing of skin.

Functional anti-aging interventions with evidence: Marine collagen peptides — Proksch 2014 RCT (n=69, Elasten collagen peptides 2.5g vs placebo x8 weeks) found 20% improvement in eye wrinkle depth and significantly improved skin elasticity; Inoue 2016 RCT confirmed 10g daily hydrolyzed collagen improved skin hydration, elasticity, and collagen density on ultrasound. Vitamin C — rate-limiting cofactor for prolyl hydroxylase and lysyl hydroxylase (collagen cross-linking enzymes); topical L-ascorbic acid 10–20% (with ferulic acid stabilizer, pH <3.5 for efficacy) is the most evidence-supported topical anti-aging active; oral vitamin C 1–3g daily maintains fibroblast collagen synthesis. Anti-glycation strategy — low-sugar, low-AGE diet (avoiding high-temperature cooked, processed meats, and commercial bakery goods with highest AGE content); benfotiamine 600mg (inhibits AGE formation); carnosine 500mg (anti-glycation dipeptide); aminoguanidine (investigational). Red and near-infrared light therapy — photobiomodulation activates mitochondrial cytochrome c oxidase, increasing ATP production in fibroblasts and keratinocytes; Wunsch 2014 RCT (n=136) found 660+830nm LED treatment significantly improved skin complexion, skin feeling, procollagen I density (29% increase), and MMP-1 reduction — the first high-quality controlled trial of LED for skin aging.

Frequently Asked Questions: Functional Dermatology

What are the best supplements for hair loss?

The most evidence-supported supplements for androgenic alopecia address underlying nutritional deficiencies and metabolic drivers: iron/ferritin repletion to ≥70 ng/mL (particularly in women — often the single most impactful intervention for female pattern hair loss); zinc 25-45mg daily (rate-limiting mineral for follicle proliferation and 5-alpha-reductase modulation); vitamin D optimization to 60-80 ng/mL (vitamin D receptors are expressed on follicle stem cells and are required for follicle cycling); marine collagen hydrolysates 2.5-10g daily (Maia Campos 2015 RCT: significant improvement in hair density at 90 days); and biotin 2,500-5,000μg (though deficiency is rare, it supports follicle keratinization). Saw palmetto (Serenoa repens) 320mg inhibits 5-alpha-reductase with a favorable side-effect profile compared to finasteride and has multiple RCTs supporting efficacy.

Can diet cure psoriasis?

Diet cannot cure psoriasis — which has a strong genetic component — but dietary modifications significantly reduce severity and frequency of flares. Mediterranean diet adherence is inversely correlated with psoriasis severity in large population studies. Gluten-free diet improves psoriasis in the 16% of patients with elevated anti-gliadin antibodies. Omega-3 fatty acids 3-4g daily (EPA+DHA) reduce PASI scores in multiple RCTs. Low-calorie, anti-inflammatory dietary patterns reduce systemic inflammation driving the IL-23/Th17 pathway. Dairy elimination and alcohol avoidance (alcohol is a potent psoriasis trigger) provide additional benefit. Dietary changes work synergistically with gut restoration (probiotics, prebiotic fiber) to reduce the gut-skin axis inflammation driving this condition.

Does diet cause acne?

Yes — high-glycemic diet and dairy consumption are the two most evidence-supported dietary acne drivers. Multiple Harvard cohort studies (combined n=47,355) found dairy — particularly skim milk — associated with acne through IGF-1 and whey protein-mediated mTORC1 activation. Three independent RCTs have demonstrated that low-glycemic diet reduces acne lesion counts by 28-66% through reducing insulin-driven IGF-1 signaling that activates sebaceous glands and follicular hyperkeratinization. Non-Westernized populations following low-glycemic, dairy-free diets have essentially zero acne prevalence. A 12-week trial of low-glycemic, dairy-free eating is the foundation of functional medicine acne treatment.

What functional medicine tests are useful for skin conditions?

High-yield functional medicine testing for skin conditions includes: fasting insulin and HOMA-IR (insulin resistance drives acne, AGA, and skin aging); comprehensive thyroid panel (thyroid dysfunction causes hair loss, dry skin, and impaired wound healing); ferritin and zinc (hair follicle function); vitamin D (immune modulation for psoriasis, follicle cycling for AGA); sex hormone panel including DHEA-S and free testosterone (androgen excess in female AGA and hormonal acne); comprehensive stool testing with intestinal permeability markers (gut-skin axis for psoriasis and acne); and anti-gliadin antibodies/tTG IgA (celiac/gluten sensitivity in psoriasis). Organic acids testing identifies nutritional deficiencies and metabolic dysfunction impacting skin health systemically.

Your skin is a systemic readout — and the most meaningful improvements in skin health come from addressing its internal drivers. If you’re struggling with hair loss, psoriasis, persistent acne, or premature skin aging that topical treatments haven’t resolved, a comprehensive functional medicine evaluation can identify the metabolic, hormonal, gut, and nutritional root causes. The Private Practice offers individualized functional dermatology programs. Call (810) 206-1402 to schedule your consultation.

Functional Dermatology: Hair Loss, Psoriasis, Acne, and Skin Aging Through Gut Health