Overview
Psoriasis is a recurring inflammatory skin condition causing thickened, scaly patches, often on the elbows, knees, scalp and lower back. Appearance varies with skin tone. Some people develop psoriatic arthritis, and psoriasis is associated with cardiometabolic conditions.
How common is it?
Psoriasis is a common long-term skin condition. It can start at any age and often follows periods of flaring and improvement.
Causes and risk factors
Psoriasis results from T-cell-mediated inflammation causing keratinocyte hyperproliferation. Genetic predisposition is triggered by environmental factors.
Common risk factors
- Family history and genetic susceptibility increase the likelihood of psoriasis.
- Triggers: streptococcal throat infection (especially guttate psoriasis), stress, skin trauma (Koebner phenomenon), alcohol, smoking, beta-blockers, lithium, antimalarials
- HIV infection (dramatically worsens psoriasis)
- Obesity increases risk and severity
Symptoms
- Raised, scaly plaques: often pink or red on lighter skin and grey or darker on brown or black skin, with pale scale.
- Dry, cracked skin that may bleed
- Itching, burning, or soreness
- Thickened, pitted, or ridged nails
- Scalp involvement: thick scaly patches beyond the hairline
- Guttate psoriasis: widespread small drop-like lesions, often triggered by streptococcal infection
- Pustular psoriasis: pus-filled blisters (rare)
- Erythrodermic psoriasis: widespread redness affecting most of the body (rare — medical emergency)
When to see a doctor
See a GP for new or worsening skin changes. Seek urgent hospital assessment for erythrodermic psoriasis (skin all over body red and inflamed) and for pustular psoriasis. Refer to rheumatology for joint pain or stiffness alongside psoriasis.
Diagnosis
Clinical diagnosis in most cases. Skin biopsy if uncertain. Distinguish from eczema, fungal infection, and lichen planus. PASI (Psoriasis Area and Severity Index) and DLQI (Dermatology Life Quality Index) quantify disease severity.
Treatments
Topical treatments
Topical treatment is selected for the site and severity, often using corticosteroids and vitamin D analogues. Follow the prescribed strength and duration; potent steroids are not suitable for the face, skin folds or genitals.
Phototherapy (narrowband UVB)
Supervised narrowband UVB phototherapy can help when topical treatment is insufficient. The schedule and response vary; it is not the same as using a sunbed.
Methotrexate and ciclosporin
Specialists may prescribe methotrexate or ciclosporin for more severe disease, with regular safety monitoring. Methotrexate for psoriasis is taken once weekly, never daily. Discuss pregnancy plans and other medicines before treatment.
Biologic therapies
Biologic medicines target parts of the immune system and can achieve substantial skin improvement. Choice, infection screening and monitoring depend on the individual; response varies by medicine and over time.
Self-care and lifestyle
- Avoid identified triggers: alcohol, smoking, stress
- Moisturise regularly to reduce scale and itching
- Attend for streptococcal throat infections promptly — tonsillitis is a common psoriasis trigger
- Maintain a healthy BMI — obesity worsens psoriasis and reduces biologic efficacy
Prevention
Psoriasis cannot reliably be prevented. Identify personal triggers and seek appropriate care for infections; antibiotics should not be used solely to prevent psoriasis flares.
Sources for targeted updates
Updated: 24 October 2026. Targeted corrections to frequency, risk factors, symptoms, treatment, prevention, overview. This update covers the named sections; a full review of the remaining guide is pending.