Psoriasis
Not a skin condition — a systemic inflammatory disease that appears on the skin
What it is
Psoriasis is a chronic, immune-mediated inflammatory disease driven by the IL-23/IL-17 pathway, in which keratinocytes proliferate far too quickly and produce the thick, scaly, well-demarcated plaques that give it away. It is not contagious, it is not dandruff, and it is not dry skin.
Why it matters
The single most important fact about psoriasis is that it is not confined to the skin. It is a systemic inflammatory disease, and the inflammation that raises plaques also raises cardiovascular risk. People with psoriasis — particularly severe psoriasis — have higher rates of cardiovascular disease, metabolic syndrome, type 2 diabetes, fatty liver, and depression, and about a third develop psoriatic arthritis, which can cause permanent joint damage if it is not caught. Treating psoriasis as a cosmetic rash means missing all of this. The skin is the visible part of a systemic problem, and it should be the prompt to look further.
What BioSignal knows about treating this
What works for Psoriasis
BioSignal’s clinical summary, most important first.
- Topical therapy for limited disease: vitamin D analogues, corticosteroids, tazarotene
- Phototherapy (narrowband UVB) for more extensive disease
- Systemic therapy: methotrexate, ciclosporin, acitretin
- Biologics targeting IL-17, IL-23 and TNF — genuinely transformative, with strong randomised evidence
- Weight loss — improves psoriasis, and improves the cardiometabolic risk that travels with it
- Treating the comorbidities: cardiovascular risk, metabolic disease, depression, psoriatic arthritis
Signal Records relevant to this condition
Interventions and contributing factors — some of these records describe a cause rather than a cure. The rating shown is BioSignal’s confidence in that Signal Record, not a claim about how well it treats this condition. Open any of them for the full evidence.
- RetinoidsHigh confidence
The best-evidenced topical in dermatology, for acne and for photoaging — and among the cheapest. Retinol is not tretinoin. Expect irritation for a few weeks. Isotretinoin is a potent teratogen; the depression and IBD links are not established.
- Omega-3 Fatty AcidsModerate confidence
Lowers triglycerides, and reduces preterm birth in pregnancy. Routine fish oil does NOT prevent cardiovascular disease, cancer or dementia in the general population. High-dose omega-3 increases atrial fibrillation risk — a real harm most bottles do not mention.
- Vitamin DHigh confidence
Effective for deficiency and for bone health in at-risk groups. For broad disease prevention in adults who are already replete, the largest trials are null — and confidence in that null is high. Routine testing of healthy adults is not supported.
- AlcoholHigh confidence
A Group 1 carcinogen with dose-dependent harms. The heart-protection belief does not survive the methods designed to test it. Cutting back helps, even without quitting.
- Curcumin (Turmeric)Limited evidence
Thousands of studies, no approved drug — because curcumin is barely absorbed and a known false positive in lab assays. Modest osteoarthritis relief is its one credible claim.
New to this? Read these first
How this usually unfolds
- Recognize risk factors
- Get diagnosed
- Track key biomarkers
- Lifestyle first
- Evidence-based treatment
- Long-term monitoring
Who is at risk
- Family history and genetic susceptibility
- Obesity — which both raises risk and worsens severity
- Smoking
- Alcohol
- Stress
- Certain medications (lithium, beta blockers, antimalarials)
- Streptococcal infection (a classic trigger for guttate psoriasis)
How it's diagnosed
Psoriasis is diagnosed clinically from the appearance and distribution of the plaques — sharply demarcated, silvery-scaled, favouring extensor surfaces, scalp, and nails. Biopsy is rarely needed. What SHOULD be routine, and often is not, is screening: for psoriatic arthritis (joint pain, stiffness, swollen digits, nail changes) and for cardiometabolic risk.
Key biomarkers
Lifestyle
Explore this condition across BioSignal
Related Foundations
Related Signal Records
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Frequently asked questions
Is psoriasis just a skin condition?
No, and this is the most important thing on the page. Psoriasis is a systemic immune-mediated inflammatory disease that happens to be visible on the skin. The same inflammation is associated with a higher risk of cardiovascular disease, metabolic syndrome, type 2 diabetes and fatty liver, and around a third of people with psoriasis develop psoriatic arthritis. If your psoriasis is being managed as a cosmetic problem, the most consequential part of the disease is going unwatched.
Is it contagious?
No. Not at all, not by touch, not by swimming pools, not by sharing anything. This is worth stating flatly because the belief is common and the social cost of it — people who will not shake hands, who stare, who move away — is one of the genuinely painful parts of living with this disease.
Is it just very dry skin or bad dandruff?
No. It looks superficially similar to dandruff on the scalp and to dry skin elsewhere, which is why it is so often self-treated with moisturisers for years before anyone gets a diagnosis. But the mechanism is entirely different: this is immune-driven over-proliferation of skin cells, not dryness. Moisturiser will not touch it, and the treatments that do are prescription treatments.
My joints hurt. Is that related?
Very possibly, and please have it looked at properly rather than waiting. Around a third of people with psoriasis develop psoriatic arthritis, and it can cause permanent joint damage if it is not treated. Morning stiffness, swollen fingers or toes, and nail changes are the signals. This is not a symptom to mention in passing at the end of an appointment about your skin.
Do the new biologics actually work?
Yes — and this is one of the more genuinely good stories in modern medicine. Biologics targeting IL-17 and IL-23 have strong randomised evidence and can produce near-complete clearance in a large proportion of people, which was simply not achievable a couple of decades ago. They are not without risks and they are not for everyone. But if you have been told for years that nothing works for psoriasis, that information is now out of date.
Evidence summary
Psoriasis is an immune-mediated inflammatory disease driven principally by the IL-23/Th17 axis. Its association with cardiovascular disease, metabolic syndrome, type 2 diabetes, MASLD, and depression is well established, and major guidelines recommend cardiometabolic risk screening in patients with psoriasis — a recommendation that is frequently not followed in practice. Approximately one third of patients develop psoriatic arthritis. Biologic therapies targeting IL-17, IL-23, and TNF have strong randomised evidence, achieving high rates of skin clearance. Weight loss improves psoriasis severity in randomised trials. Smoking and alcohol are associated with worse disease. It is not infectious and is not caused by poor hygiene or dry skin.
References & sources
- AAD-NPF guidelines for the management and treatment of psoriasis
- NICE guideline: Psoriasis — assessment and management
- Joint AAD/NPF guidance on comorbidity screening in psoriasis
Educational information — not medical advice
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