Psoriasis: Get informed

Psoriasis is a chronic inflammatory disease, mainly affecting the skin.

PSORIASIS: Definition, symptoms, treatment

What is psoriasis? 


Psoriasis is a chronic inflammatory skin condition. It is an autoimmune disease characterized by the appearance of red patches, covered with silvery scales that come off from the skin.

This disease is caused by the immune system malfunction, which results in chronic and exaggerated inflammation of the skin (which becomes red) and an overproduction of epidermal cells (epidermis is the surface layer of the skin): the keratinocytes. Due to the accumulation and accelerated maturation of these cells, the skin becomes thicker: this is called hyperkeratosis.

Psoriasis progresses by flare-ups of different frequency and intensity, interspersed with periods of remission that can last for several years.

It is non-contagious and most often benign, but some patients can develop moderate to severe forms of psoriasis, with possible damage to other organs such as joints, cardiovascular system or the mucous membranes.

Psoriasis can have a significant psychological impact, and depending on the location and extent of psoriatic lesions, the condition can alter the patient's quality of life.

Is psoriasis a common disease?

Psoriasis is a condition that affects around 125 million people, that is about 2.2% of the world's population. Its prevalence is greater in industrialised countries and in those far from the equator.

In the UK, around 1.8 million people have psoriasis, or about 2% of the population. 

This disease affects both men and women, and can occur at any age, but most often develops in adults aged between 20 and 40.

About 30% of patients suffer from psoriatic arthritis, in addition to the cutaneous form of the disease.

Psoriasis symptoms and possible complications

Different forms of psoriasis

  • Plaque psoriasis, also called psoriasis vulgaris, is the most common form (over 80% of all cases). It is characterized by red patches, well defined and covered with scales (white films that break off from the skin). They can cause itching or pain, and are mainly located in areas where skin-to-skin friction occurs (elbows, forearms, knees…).
  • Scalp psoriasis affects 50 to 80% of adult plaque psoriasis cases, but can also be isolated. It is difficult to treat and it can spread over the forehead, behind the ears and to the back of the neck. This form of psoriasis is very itchy, and it becomes visible when the scales come off, so the impact of the condition on the patient’s social life is significant.
  • Nail, or ungual psoriasis is diagnosed in 50% of patients already suffering with psoriasis. It is characterized by the presence of tiny dents on the surface of the nail (called “nail pits”), the separation of the nail from the nail bed, spots, thickening, or ridges. This form is uncomfortable for patients, both from the aesthetical and practical point of view.
  • Guttate psoriasis is much rarer (less than 10% of cases) and often occurs in children and teenagers. It appears as a multitude of small plaques, less than 1 millimeter in diameter, mainly at the trunk. It usually develops after a strep infection (for example after a sore throat) and can sometimes progress to chronic plaque psoriasis.
  • Pustular psoriasis is characterized by the presence of pustules on the red patches. They do not contain germs. They can be located on the hands and feet (this is called palmoplantar psoriasis), or on the fingertips (this is called acrodermatitis continua of Hallopeau).
  • Erythrodermic psoriasis is a very serious and rare generalised form of psoriasis that can affect the entire surface of the skin. It is usually accompanied by fever and shivering, and needs to be treated quickly.
  • Inverted, or intertriginous psoriasis is characterized by the appearance of well-defined red patches. They are found in skin folds: in the armpits, groin, navel, under the breasts, in the stomach folds or between the buttocks. There is no scale, as it is wiped out by perspiration. This form is often mistakenly confused with a yeast infection (infection with fungi).
  • Facial psoriasis affects the hairline and the nasolabial folds. This form of psoriasis is difficult to live with, as it is quite visible. However, the face is rarely affected by psoriasis.
  • Mucosal psoriasis is a rare form that can affect the genital mucous membranes (glans, vulva, vagina) as well as the mouth (tongue and the inside of the cheeks). It can have a significant negative impact on the patient's sex life.

Psoriasis complications

About 8 to 10% of people affected by psoriasis suffer from painful joints, particularly in the hands and feet, or in the pelvis and spine. This disorder is called psoriatic arthritis, the onset of which comes months or even years after the skin symptoms appear. Its symptoms, treatments and care plan are similar to those of rheumatoid arthritis and ankylosing spondylitis.

In addition, for patients with severe psoriasis, social (aesthetic and psychological) and  professional consequences are significant and can lead to depression in 30 to 40% of cases.

Finally, psoriasis is often associated with the development of a metabolic disorder (a disorder that affects the production of energy in cells) and of type 2 diabetes. Patients are also twice as likely to have cardiovascular complications (atherosclerosis, heart attack…).

Causes of psoriasis and its risk factors 

First of all, there is a genetic predisposition to psoriasis in around 30% of cases (1 in 3 patients have a family member suffering with the same disease). Several genes have thus been identified and associated with the increased occurrence of psoriasis (for example, the PSORS1 gene).

Also, various environmental factors, associated with the genetic predisposition, have been identified:

  • skin irritations: rubbing, scratching, pricking, wounds (this is called "Köbner  phenomenon", when new lesions appear on healthy skin that has just suffered a trauma);
  • sunburns (although moderate and regular exposure to sunlight improves psoriasis symptoms);
  • cold and dry environment, as well as pollution;
  • fatigue, stress or emotional shock;
  • infection: streptococcus (ENT infection, angina) or HIV / AIDS;
  • excessive consumption of tobacco and alcohol;
  • certain medications: malaria drugs (chloroquine and hydroxychloroquine), antihypertensives (beta blockers, ACE inhibitors), treatments for bipolar disorder (lithium), multiple sclerosis or hepatitis C (interferons). In addition, the sudden cessation of corticosteroid therapy may make psoriasis worse.

Diagnosing psoriasis 

The diagnosis of psoriasis is essentially based on a clinical examination by a dermatologist. The latter inspects the appearance and location of the lesions (scalp, knees, elbows, lumbar region and nails in particular).

In some cases, a biopsy (removing a small sample of skin under local anesthesia) may be done to rule out other possible causes of the skin condition (eczema, yeast infection) and thus confirm the diagnosis of psoriasis.

The diagnosis is therefore based on 3 criteria:

  • thickening of the surface layer of the skin (epidermis) due to excessive multiplication and accumulation of keratinocytes;
  • a large number of capillaries (small blood vessels) giving the skin its red color;
  • the accumulation of white blood cells (inflammation cells) in the epidermis, which can lead to the development of pustules.

Different scores are used to assess the severity of the disease:

  • the PASI score (Psoriasis Area and Severity Index) assesses in particular the appearance of the skin, taking into account the area affected (the percentage of the total surface of the body) and the intensity of redness, thickness and scaling of the lesions. It varies from 0 (no severity) to 72 (maximum severity).
  • the DLQI score (Dermatology Life Quality Index) assesses the patient's quality of life. About ten questions are asked: aesthetic impact, impact on work and leisure, as well as on love, sex and family life, etc. It varies from 0 (no impact) to 30 (severely reduced quality of life).

Treatments for psoriasis 

Psoriasis is a condition that cannot be cured. But there are various topical and systemic treatments that can ease the symptoms and improve patients’ quality of life.

Topical treatments

Topical corticosteroids are cortisone-based products that help fight psoriasis inflammation. Their form varies according to the location and appearance of the lesions: ointments are used to treat very dry and thick patches, creams are prescribed for lesions with few scales, for folds or mucous membranes, and finally, scalp psoriasis is treated with lotions (Betnovate®).

In addition, topical corticosteroids are divided into several classes, depending on their strength: ointments and creams based on the so-called strong corticosteroids are used on thick areas of the skin, such as elbows or knees (Diprosone®, Locoid®, Nerisone ® , Clarelux®, Dermovate® or Calcipotriol/Betamethazone®) and weak corticosteroids are used on the face (Locapred®, Locatop®, Tridesilon®).

They are generally applied daily and the duration of use should be limited. They are contraindicated in the event of skin ulcers or infections. Certain side-effects may be observed, depending on the activity of the substance, or the amount of treatment used: thinning of the skin, stretch marks, rosacea, redness (especially when applied to the face) or, more rarely, localised depigmentation of the skin, body hair growth or eczema.

Vitamin D3 analogues prevent the excessive multiplication of keratinocytes. There are, for example, calcipotriol (Dovonex®)and calcitriol (Silkis®), which require two applications per day. They work less quickly but are better tolerated than topical corticosteroids, although they can be irritating at the start of the treatment. They are therefore used as a maintenance treatment for psoriasis.

The maximum dose per week prescribed by the doctor to avoid the risk of calcium excess in the blood or urine, should not be exceeded.

The combination of a vitamin D3 analogue with a topical corticosteroid (Dovobet®, Xamiol®, Enstilar®) is very effective in the treatment of acute flare-ups of psoriasis (1 daily application for a maximum of 4 weeks). It can be used at a lower dose as a maintenance treatment (one application per week).

Salicylic acid is able to dissolve the surface layer (or cornea) of the epidermis. It is used in combination with a fatty excipient (Vaseline) to sand off the most scaly lesions of psoriasis.

Finally, tazarotene (Zorac®) is used in localised psoriasis. This topical retinoid is contraindicated during pregnancy.


Phototherapy is considered when psoriasis affects a large area of ​​the body or when the lesions persist despite local treatment. Ultraviolet rays help slow the growth of skin cells and relieve inflammation.

There are 2 types of phototherapy:

  • PUVA therapy uses UVA rays combined with a photosensitizing drug (Oxsoralen®, a psoralen). Two hours must pass between taking this medication and being exposed to UV rays. The number of PUVA-therapy courses is limited to ten.
  • UVB phototherapy does not require photosensitizing medication and generally consists of 3 sessions per week for the first 2 months, then 1 to 2 sessions per week for maintenance, for several months.

The duration of light therapy is limited because of the risk of developing skin cancer (melanoma). During each session, the patient is required to wear opaque glasses to protect the eyes from the risk of cataracts, and appropriate clothing (briefs) to protect the genitals. Finally, it is not generally used in children under 12.

The sessions are prescribed by a dermatologist and take place at the doctor’s surgery or at a hospital.

Systemic treatments for psoriasis

Systemic or general treatments for psoriasis include several types of drugs:

  • an oral retinoid, that regulates skin renewal: acitretin;
  • immunosuppressants, that reduce the activity of the immune system, such as methotrexate or ciclosporin;
  • biotherapies , that block the action of certain immune substances such as TNF (Tumor Necrosis Factor).

Acitretin is a derivative of vitamin A synthesis, used in severe forms of psoriasis. It is administered orally once a day and can be used in combination with phototherapy. It has a teratogenic risk (malformation of the foetus during pregnancy): it is therefore mandatory for all women of childbearing age to perform a pregnancy test before treatment, and to use effective contraception, before starting the treatment, during treatment, and during the first 3 years after stopping the treatment. It is also forbidden to drink alcohol during treatment and for 2 months after stopping it.

Methotrexate is used for severe forms of psoriasis, but also for certain chronic rheumatisms, such as psoriatic arthritis. It is taken once a week, orally (Maxtrex®, intramuscularly or subcutaneously (Metoject®, Prexate®, Zlatal®) and requires regular hepatic, renal and blood monitoring. The most common side effects are dizzy spells, digestive disorders, low white blood cells and inflammation of the mouth. Taking a folic acid supplement, but not at the same time as methotrexate, makes it possible to reduce the frequency of some of these side effects. Finally, methotrexate has a teratogenic risk (malformation of the foetus during pregnancy). Effective contraception in women of childbearing age taking this treatment is therefore necessary, and when a desire to become pregnant appears, the patient should make an appointment with her attending physician in order to adapt the treatments; a certain period of time must pass between stopping the treatment and conception.

Ciclosporine is an immunosuppressant, with efficiency comparable to methotrexate, used for severe forms of psoriasis. It requires 1 daily oral intake (for a maximum of one or two years due to its renal toxicity). Regular monitoring of blood pressure and kidney function (by blood tests) should be performed.

Apremilast (Otezla®) is an immunosuppressive drug used in case of treatment failure, contraindication, or intolerance to other psoriasis treatments. Its daily dose is 1 tablet. Digestive disorders (diarrhoea, nausea) may be observed at the start of treatment. The patient should report the existence or appearance of depression or insomnia to his or her doctor.

Finally, biotherapies (treatments with living organisms or substances derived from these organisms) are prescribed as a second-line treatment, in the event of a contraindication or in the absence of response to usual treatments. They require a thorough medical check-up (especially dental) prior to initiating treatment and their initial prescription is reserved for hospital doctors.

Anti-TNFα are biotherapy drugs most often used for psoriasis. TNF (Tumor Necrosis Factor) is a protein involved in inflammation, which is excessively produced by patients with psoriatic arthritis. By binding to TNF, these drugs block its activity and reduce inflammatory reactions.

These drugs are injected: via infusion like infliximab (Remicade®) or subcutaneously like etanercept (Enbrel®), adalimumab (Humira®) and certolizumab (Cimzia®). 75% of the symptoms disappear in more than ⅔ of the patients having taken these treatments.

Other biotherapies are also used, such as the interleukin inhibitors, molecules that are involved in the inflammation process. These include brodalumab (Kyntheum), ixekinumab (Taltz®), guselkumab (Tremfya®), ustekinumab (Stelara®), secukinumab (Cosentyx®) and rizankizumab (Skyrizi®). These drugs come in injectable forms, and are administered subcutaneously.

These biotherapies require regular medical supervision because of their side effects, and especially because of the risk of infection. If you observe any sign of infection, such as fever (even low) or weight loss (even moderate), you should tell your doctor as soon as possible. An untreated infection can have very serious consequences in people treated by biotherapies.

Other treatments

Besides drug treatments, other types of treatment can reduce the frequency and severity of psoriasis flare-ups and improve patients’ quality of life.

Hydrating the skin is essential to avoid irritation and to cope with different types of external aggression (sun, cold, pollution, friction, etc.). Thus, skin moisturizers, or emollients, help reduce skin dryness and prevent the formation of scales.

The use of a moisturizing cream or milk (half-watery, half-oily formulas that help maintain the hydrolipidic film of the epidermis) is recommended during the hottest periods, and a balm (thicker texture, mainly based on oil and butter, which repairs and heals dehydrated and very dry skin) for cold weather. The use of a balm is also recommended in the evening.

These products are particularly beneficial to patients using treatments that dry the skin (acitretin), and to those being treated with PUVA therapy.

Spa treatments can also have a beneficial effect on patients with psoriasis. The properties of water vary from centre to centre: it can be rich in selenium, arsenic, bicarbonate and sodium, or even sulfur. Various hydrothermal treatments (baths, showers, massages, etc.) help relieve dryness, hydrate the skin, soothe the itching and heal the plaques.

Such spa centres are also a great place to get advice and support from health professionals, which can help the patient relieve his or her symptoms, and acquire more independence in the management of his or her disease. Moreover, patients get to meet other patients, their families and carers, as well as patient associations, which helps them feel understood and  less alone.

Living with psoriasis

Follow-up visits

The frequency of medical visits and biological examinations is established with the attending physician, dermatologist and possibly rheumatologist, if the patient also suffers from psoriatic arthritis.

It is recommended to see your doctor every 3 months at the start of treatment, to assess its effectiveness, then the appointments can be spaced out, if the treatment is well tolerated.

Since psoriasis treatments are long-term ones, it is necessary to create a trusting relationship with your physician. It is important to understand and follow your treatment plan properly:

  • Do not stop treatment without prior medical advice;
  • Do not exceed the prescribed dose, even for topical treatments (creams, ointments, lotions);
  • Let your doctor know of any side effects from the very beginning, so that he or she could adjust your treatment;
  • Do not interrupt contraception, if it is necessary for the prescription of a drug (acitretin, methotrexate), and tell your doctor if you are planning a pregnancy;
  • Tell your doctor straight away if you notice any unusual signs of infection (discharge  from a psoriasis lesion, fever, ENT infection, etc.).

Good communication with your doctor helps identify and avoid any triggers and aggravating factors of your condition (medication, rubbing the skin areas that are at risk, stress, smoking, etc.)

Some tips for everyday life:

  • Hydrate your skin well, about twice a day, using suitable creams, milk or balms (prefer those based on cold cream or Galen's cerate), especially after bathing or showering, or exposure to the sun;
  • Avoid skin irritation (prefer loose, comfortable clothes, made of natural materials such as cotton, linen or silk);
  • Avoid skin wounds (cuts, scratches, grazes) which can cause psoriatic lesions;
  • When taking a bath/shower, choose a gentle superfatted soap, or a shower or bath oil. Choose hypoallergenic products and mild shampoos. Do not use scrubs or washcloths (soap with your hands);
  • Do not take hot showers or baths (the temperature should be ≤ 36 ° C) because hot water dries the skin and can trigger a flare-up;
  • Add wheat or oatmeal starch, or oil, to soothe itching and soften the skin, and sea salt for scaly skin;
  • Make-up is not contraindicated for patients with psoriasis, but only high-quality hypoallergenic and non-irritating products should be used;
  • Protect yourself from sunburns;
  • Stop smoking and consume alcohol in moderation;
  • Have a healthy lifestyle: drink water regularly (about 2L per day) and eat a balanced diet (avoid processed foods that contain trans-fatty acids and refined sugars such as cakes, nuggets, cereals and sodas, and prefer raw foods such as fruit and vegetables, but also oily fish full of good unsaturated fats);
  • Relaxation techniques (sophrology, yoga, tai chi, acupuncture, massages, etc.) can help reduce stress and the frequency of psoriasis flare-ups;
  • Psychological support may be necessary to help the patient cope with various psychological and social consequences of the disease;
  • Joining a patient support group or a social network for patients will allow you to meet other people suffering with the same disease, and thus exchange advice and find support;
  • Do not take any medication without medical advice.

To sum up, psoriasis is a chronic inflammatory condition. It mainly causes skin damage, but can also affect other organs, provoking joint pain (psoriatic arthritis), metabolic disorders (type 2 diabetes) and cardiovascular diseases (myocardial infarction). This disease can have a serious impact on the patient’s quality of life, especially in terms of psychological health and social interactions. However, the existing treatments, in particular the new biotherapies, make it possible to ease the symptoms and prevent exacerbations.

avatar Alexandre Moreau

Author: Alexandre Moreau, Digital Marketing Assistant

Within the Digital Marketing team, Alexandre is in charge of writing medical factsheets and scientific articles. He is also in charge of leading and moderating the community on the forum, in order to ensure optimal... >> Learn more

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