psoriasis blood test explained

Overview

Psoriasis is a long-lasting skin condition where the body makes new skin cells too quickly. This causes raised, red, scaly patches on the skin. It is not contagious — you cannot catch it from someone else.

Yes, psoriasis is fairly common. It affects about 2–3% of people worldwide.

Psoriasis can affect anyone at any age, but it most often starts between ages 15 and 35. Both men and women get it, and it runs in some families.

Symptoms

Common symptoms

• Red, raised patches of skin covered with silvery-white scales
• Itching, burning, or soreness on the affected skin
• Dry, cracked skin that may bleed
• Thick, pitted, or ridged fingernails and toenails
• Stiff, swollen joints (this can be a sign of psoriatic arthritis)

Symptoms in children

• Smaller, smoother patches of red skin, often in the diaper area
• Scalp psoriasis that looks like dandruff
• Pitted or separated nails
• Irritability from discomfort or itching

Symptoms in older adults

• Thinner, less scaly patches that may be mistaken for eczema
• More frequent involvement of the nails and joints
• Dry, itchy skin that can be harder to treat because of other health conditions

Causes

Main causes

• Psoriasis is an autoimmune condition — your immune system mistakenly attacks healthy skin cells, causing them to grow too quickly.
• Genes play a role — if a close family member has psoriasis, you are more likely to develop it.

Risk factors

• Having a family history of psoriasis
• Stress, which can trigger or worsen flare-ups
• Infections, especially strep throat (linked to a type of psoriasis called guttate)
• Injury to the skin, such as a cut, scratch, or sunburn (Koebner phenomenon)
• Certain medications, including lithium, beta-blockers, and antimalarial drugs
• Smoking and heavy alcohol use

When to see a doctor

See a doctor urgently if:

• If you have a widespread rash with pus-filled bumps and feel very unwell (fever, chills)
• If you have severe joint pain and stiffness that interferes with daily activities
• If you notice signs of infection in your skin: spreading redness, warmth, or pus

Book a routine appointment if:

• If you have patches of scaly skin that do not go away with over-the-counter moisturisers
• If you are concerned about changes in your nails
• If joint pain or swelling develops along with skin symptoms

Diagnosis

A doctor or dermatologist (skin specialist) can usually diagnose psoriasis by looking at your skin, scalp, and nails. They will also ask about your symptoms, family history, and any triggers.

Tests that may be done

• Physical exam: The doctor examines the affected skin and checks for typical scales and patches.
• Skin biopsy: The doctor numbs the area and removes a tiny piece of skin to examine under a microscope. This helps confirm the diagnosis and rule out other conditions.
• Blood tests: There is no specific blood test for psoriasis. However, blood tests may be done to rule out other causes of your symptoms, such as infection or arthritis. Tests may include a complete blood count (CBC), measures of inflammation (CRP or ESR), or tests for certain antibodies if psoriatic arthritis is suspected.

What to expect at your appointment

The diagnosis is usually straightforward. The doctor may take a small skin sample (biopsy) if the appearance is not clear. Results from a biopsy take about a week. Blood test results are often ready in a few days. Your doctor will explain the findings and discuss treatment options with you.

Treatment

Psoriasis treatment aims to slow skin cell growth and reduce inflammation. The right treatment depends on the type, location, and severity of your psoriasis, as well as your overall health. Most people start with topical treatments and move to stronger options if needed.

Self-care at home

• Keep your skin well-moisturised with fragrance-free creams or ointments.
• Avoid scratching or picking at scales — this can make psoriasis worse.
• Use gentle, unscented soaps and lukewarm water for bathing.
• Manage stress with relaxation techniques, exercise, or talking to a counsellor.
• Protect your skin from sunburn — moderate sunlight can help, but too much sun can worsen it.

Medical treatments

Your doctor may recommend treatments applied to the skin (topical therapies), light therapy (phototherapy), or oral or injected medications that work throughout the body (systemic therapies). These medicines aim to calm the immune system and slow skin cell growth. The choice of treatment is individualised and should be discussed with your healthcare provider. Do not change or stop treatments without medical advice.

When is surgery considered?

Surgery is not used to treat psoriasis itself. However, if you develop joint damage from psoriatic arthritis, joint replacement surgery may be considered in advanced cases, after consulting a rheumatologist.

Living with this condition

Living with psoriasis means managing flare-ups and maintaining a routine that keeps your skin comfortable. Many people find that tracking their triggers (such as stress, certain foods, or weather changes) helps them stay ahead of symptoms. With treatment, most people can keep their skin clear or nearly clear.

Lifestyle tips

• Adopt a consistent skin care routine with gentle products.
• Wear soft, breathable fabrics like cotton to reduce irritation.
• Avoid smoking and limit alcohol — both can make psoriasis worse.
• Find healthy ways to cope with stress, such as yoga, meditation, or hobbies.

Diet and exercise

There is no specific diet proven to cure psoriasis, but eating a balanced diet rich in fruits, vegetables, whole grains, and omega-3 fatty acids (found in fish) may help reduce inflammation. Regular exercise can lower stress and improve joint health if you have psoriatic arthritis. Staying at a healthy weight can also reduce the severity of symptoms.

Mental health and emotional wellbeing

Psoriasis can affect your emotional well-being because of its visible nature and discomfort. Many people feel self-conscious, anxious, or depressed. It is important to talk to your doctor about these feelings. If you are struggling, remember that help is available. If you have thoughts of harming yourself, call a crisis helpline or your local emergency services immediately.

Prevention

Psoriasis cannot be prevented because it is partly genetic. However, you may be able to reduce flare-ups by avoiding known triggers and adopting a healthy lifestyle.

Screening programmes

There is no routine screening for psoriasis. However, if you have psoriasis, your doctor may periodically check for signs of psoriatic arthritis, such as joint pain and swelling, so that treatment can start early.

Complications

If left untreated

• Psoriatic arthritis — joint inflammation that can lead to permanent joint damage if not treated
• Skin infections from scratching or cracked skin
• Nail changes that can be painful or affect hand function
• Increased risk of other health conditions, such as heart disease, diabetes, and depression

Long-term outlook

With proper treatment and care, most people with psoriasis can control their symptoms and have a good quality of life. While it is a lifelong condition, modern treatments are very effective. Many people find a regimen that keeps their skin clear or nearly clear for long periods. Working closely with your healthcare team gives you the best chance of managing the condition well.

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