Raised, well-defined plaques
Thick patches with sharp edges, often on both sides of the body.
An overactive immune system tells skin cells to grow many times faster than normal — building raised, scaly plaques that come and go.
Medical review pending
Review date to come
Key Facts
2–3%
of people worldwide live with psoriasis — about 125 million people.
3–5 days
for a skin cell to reach the surface in a plaque, versus about 28 days normally.
1 in 3
people with psoriasis develop psoriatic arthritis.
0%
contagious. You can’t catch it or spread it by touch.
What Is It?
Psoriasis is a long-term inflammatory disease. Immune cells send the wrong signals, and skin cells respond by multiplying far too quickly. The extra cells pile up into thick, scaly patches called plaques.
It usually flares and settles in cycles. It can start at any age, but most often appears between 15–35 or 50–60.
At a glance
Lifelong, with flares and calmer periods.
T cells and IL-17, IL-23 and TNF signals.
Linked to joint, heart and metabolic health.
Modern options clear most people’s skin.
Symptoms
Thick patches with sharp edges, often on both sides of the body.
Flakes that lift off, sometimes leaving tiny bleeding points.
Most people itch, and plaques can sting or feel tight.
Plaques over joints may split and bleed.
Pitting, yellow-brown “oil drop” spots, lifting.
Morning stiffness or swollen fingers — tell your doctor.
Subtypes
Most people have one main type, but types can overlap or change over time.
80–90% of cases. Thick, scaly plaques.
~8% Small drop-like spots, often after strep throat.
3–7% Smooth, shiny patches in skin folds — little scale.
~3% Rare. Pus-filled bumps on palms, soles or widespread.
1–2% Rare and urgent. Red, peeling skin over most of the body.
Important. Seek care the same day if redness covers most of your body, or you have widespread pustules with fever, chills or feeling unwell.
Across Skin Tones
On darker skin, psoriasis often looks violet, gray or dark brown, and it is more likely to leave lasting dark or light marks after it heals.
Pink to red plaques with silvery-white scale.
Salmon to red-brown with silvery-white scale.
Violet to purple-brown with gray scale.
Dark brown or purple; marks may linger for months.
Swatches are illustrations until the four clinical photos are added.
Causes & Risk Factors
About 1 in 3 people with psoriasis has a close relative with it. Gene variants such as HLA-C*06:02 raise the risk.
What's Happening in the Skin · Interactive
Step through what happens beneath a psoriasis plaque — and where each kind of treatment steps in.
New skin cells form at the base of the epidermis and take about 28 days to rise, flatten and shed.
Normal cycle: about 4 weeks
In people with an inherited tendency, strep throat, stress or a skin injury wakes up immune “alarm” cells in the dermis.
Avoiding your triggers lowers flare risk
Alarm cells release IL-23, which drives T cells to pour out IL-17 and TNF. These signals tell skin cells to multiply.
Biologics block IL-17, IL-23 or TNF here
Skin cells divide so fast they reach the surface in 3–5 days instead of about 28. The epidermis thickens.
Vitamin D creams slow this turnover
Immature cells pile up as silvery scale, and widened blood vessels make the patch red and raised.
Steroids calm it; salicylic acid lifts scale
Triggers & Aggravating Factors
Triggers differ from person to person. A simple flare diary for 2–3 months is the best way to find yours.
New plaques that form along a scratch or wound are called the Koebner phenomenon.
Losing weight, if you carry extra weight, can improve psoriasis and help treatments work better.
Daily Care & Prevention
It can trigger new plaques.
Linked to more severe disease.
Flares and treatment safety.
A common flare trigger.
Treatments
Doctors usually start with creams for limited psoriasis and move to light, pills or injections when it covers more skin, affects the joints, or doesn’t respond.
Softens and lifts scale so other treatments can get in.
Slows skin cell growth; shampoos, creams and bath solutions.
Mild steroid; helps itch on thin skin, rarely enough alone.
Ointments and urea creams reduce dryness and cracking.
Fast relief of redness and scale. Strength matched to body site.
Calcipotriene slows skin cell growth; often combined with a steroid.
Non-steroid cream applied once daily.
Non-steroid PDE4 cream, gentle enough for folds and face.
Off-label for face and skin folds where steroids thin skin.
Topical retinoid; can irritate, avoid in pregnancy.
Weekly pill or shot. Also helps joints. Needs blood tests.
Twice-daily pill; no routine blood tests.
Once-daily TYK2 inhibitor pill.
Works quickly; used short-term for severe flares.
Oral retinoid, useful for pustular types. Not for pregnancy.
Guselkumab, risankizumab, tildrakizumab. Dosed every 8–12 weeks.
Secukinumab, ixekizumab, bimekizumab. Very fast clearing.
Adalimumab, etanercept, infliximab. Also treat arthritis.
Ustekinumab, every 12 weeks after loading doses.
2–3 sessions a week in a clinic or with a home unit.
Targets a few stubborn plaques, scalp or palms.
Psoralen plus UVA; effective but used less due to skin cancer risk.
Outlook
There’s no cure yet, but most people reach clear or almost-clear skin with the right plan. Expect periods of flares and quieter stretches.
Usually by examining skin, scalp and nails. A biopsy is rarely needed.
Creams and ointments usually show clear improvement.
Typical check-in point for pills, light therapy and biologics.
Maintenance keeps flares rare; plans are adjusted over time.
Complications
The same inflammation can affect other parts of the body. Treating psoriasis well may lower some of these risks.
Up to 30% of people. Joint pain, swelling, heel pain, “sausage” fingers. Early treatment prevents damage.
Higher risk of heart attack and stroke, especially with severe psoriasis.
Higher rates of type 2 diabetes, high blood pressure, high cholesterol and fatty liver.
Common, and worth raising with your doctor. Support helps.
Crohn’s disease and ulcerative colitis are more common.
Uveitis — a painful red eye or blurry vision needs prompt care.
Lookalikes
Itchier, blurrier edges, often in elbow and knee creases rather than on the outside.
Greasy, yellowish flakes on the scalp, eyebrows and sides of the nose.
A ring with a clearer center that slowly spreads outward. A skin scraping confirms it.
Starts with one larger “herald” patch, then oval spots; fades in 6–8 weeks.
Common Questions
No. You can’t catch psoriasis from touching someone, sharing towels or swimming together.
Not yet. But many people reach clear or almost-clear skin and stay that way with ongoing treatment.
No single diet cures psoriasis. Losing extra weight and limiting alcohol can reduce severity and help treatments work.
Genes play a big role — about a third of people have a family member with psoriasis — but not everyone with the genes gets it.
For most people, yes. They slightly raise infection risk, so you’ll be screened for TB and hepatitis first and monitored over time.
If over-the-counter care hasn’t helped in a few weeks, it’s spreading, it affects your nails or scalp, or your joints ache.
References
Dermapedia is for education only and is not medical advice. It does not create a doctor–patient relationship. Always consult a qualified clinician about your own skin.