HealthInfo Waitaha Canterbury
Psoriasis
Mate tongatonga uri
Psoriasis is a long-term (chronic), common skin condition that can come and go throughout your lifetime. It can also affect your joints and nails.
It is not infectious, meaning you cannot catch it from other people.
Psoriasis can appear at any age and affects men and women.
Causes of psoriasis
Skin cells are usually replaced every 21 to 28 days. Your body makes new skin cells just under the surface to replace the old skin cells that are dropped off (shed). With psoriasis you make new skin much faster – in only a few days. This causes your skin to get thicker in places, forming rough, red areas and often silvery scales known as plaques.
Although the process is not fully understood, it is caused by a problem with the immune system.
Genetics also appear to play a part in causing psoriasis because the condition can run in whānau (families).
Certain things can trigger psoriasis or cause a flare-up. These include, stress, anxiety, some skin and throat infections, smoking, excessive alcohol and certain medicines.
Symptoms of psoriasis
The severity of psoriasis varies. Some people have minimal effects and for others it severely impacts their lives.
Symptoms include:
- Patches of rough, red skin and silvery white scales called plaques that last for weeks to months.
On darker skin, the patches may appear purple with grey scales. Scalp, elbows and knees are the most commonly affected sites.
When psoriatic plaques clear up, they may leave brown or pale marks that usually fade over several months.
Patches can form in areas where skin has been damaged such as on scars or burns.
- Itchy skin. This is usually mild but can be severe.
Fingernails can be affected, causing the nail to lift away from the finger. This can be painful.
There are several types of psoriasis, varying by the area of your body affected and the type of rash. Chronic plaque psoriasis is by far the most common, causing plaques greater then 3 cm wide.
Some people with psoriasis will develop joint problems. This is called psoriatic arthritis and is a type of inflammatory arthritis.
Diagnosing psoriasis
Usually, your general practice team diagnoses psoriasis based on the appearance of your skin. They will ask you about which body areas are affected, how it impacts your day-to-day life and if you have any joint pain. They will examine your skin, scalp and nails.
Occasionally, you will need to have a biopsy. This is when a small sample of skin is taken and examined under a microscope.
Self-care for psoriasis
Avoid putting pressure on any areas of your body affected by psoriasis. For example, if you have psoriasis on your knees, avoid kneeling.
Smoking and alcohol can make psoriasis worse. Stop smoking if you smoke and reduce your alcohol intake.
Get sunshine in small doses to help clear psoriasis. Take care to avoid sunburn as this can cause flare-ups and lead to skin cancer. Avoid sun beds.
Psoriasis can have a big effect on your quality of life, causing anxiety and depression. Speak to your general practice team if you are concerned about the impact it is having on you.
Treating psoriasis
Although there is no cure for your psoriasis, there are many effective treatments that can keep your psoriasis under control.
You often need to try different treatments to see what works for you.
Treatments depend on your symptoms and include the following:
Topical treatments
Topical treatments are products you put on your skin, such as:
- Moisturisers. These are used to help with dryness and itch, make plaques less thick and help your skin absorb other treatments. You should use them instead of soap when you wash and put them on your skin every day.
- Coal tar preparations.
- Steroids. These help by reducing inflammation, making your skin less red and itchy. Different strengths are used depending on how bad your psoriasis is and which part of your body it is on.
- Vitamin D-like compounds. These reduce the thickness and scaliness of plaques. Calcipotriol and calcitriol are examples of these creams.
- Combination calcipotriol/betamethasone dipropionate ointment, gel or foam. This may be used if an individual cream has not worked.
- Tar shampoos and scalp lotions. These are used on your scalp. Coco-scalp is a product used for severe plaques.
Other treatments for psoriasis
If your psoriasis is very bad and not getting better with topical treatment, your general practice team may refer you to see a specialist skin doctor (a dermatologist).
Your treatment may then include:
- A course of ultraviolet light treatment that works by reducing inflammation of the skin.
- Medicines that suppress your immune system and reduce inflammation. For example, ciclosporin or methotrexate.
- Acitretin. This is a type of medicine called a retinoid, which means it is similar to vitamin A. It works by slowing down skin production. You must not take it if you are pregnant or trying to get pregnant, as it can cause serious damage to a developing baby. You cannot donate blood while taking this medication, or for 2 years afterwards.
HealthInfo recommends the following pages
- DermNet NZ – Psoriasis
Detailed information and images of psoriasis.
- NHS – Psoriasis
More detailed information about psoriasis.
Written by HealthInfo clinical advisers. Last reviewed February 2025.
SourcesReview key: HIPSO-20776
