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Différences eczéma et psoriasis.

Eczema versus Psoriasis: What are the Similarities and Differences?

Eczema and psoriasis are both skin conditions. Although they have similarities, these conditions also have differences. Let's explore them together in this article.

Version relue et validée par la dermatologue, Dr. B. LEVY GAREL (France).

Eczema and Psoriasis: What should we know about these two diseases?

There are numerous causes and forms of eczema. To simplify our explanation, we will focus on the most common ones:

  • The atopic dermatitis.

    Second only to acne, atopic dermatitis is a chronic inflammatory disease with multifactorial origins and a significant genetic component. This disease can affect people of all ages, but it primarily affects infants starting from 3 months old and tends to improve or even disappear before puberty. However, it persists into adulthood in about 10% of cases. It is characterized by patches of eczema (which we will detail later) associated with a general skin dryness.

  • Thecontact eczema :

    This refers to an allergic reaction of the skin to an external substance that comes into contact with it. Therefore, eczema is localized on the areas that have been affected by the product that caused the allergy.

Thepsoriasisis a chronic inflammatory skin disease that affects approximately 2% of the French population. It is characterized by the appearance of thick red patches covered with white dead skin known as scales. These patches can be more or less itchy.

These two skin diseases exhibit several similarities, both in terms of their causes and their manifestations.

The similarities between these two diseases.

  • Similar causes.

    Theatopic eczema is promoted by agenetically originated atopic predisposition. In most cases, a child who is affected has a parent who suffers from atopy, that is to say atopic eczema, asthma or allergic rhinitis, also known as hay fever. Atopy refers to a person's tendency to develop aallergic reaction to normal environmental elements (animal hair, dust, pollen...), which do not cause problems for the rest of the population. Studies have highlightedabnormalities affecting the gene coding for filaggrin, as well as other molecules necessary for the proper functioning of the corneal layer. This atopy is caused by adysfunction of the skin barrier, due to a lack of sebum, lipids and cell adhesion molecules production, which can no longer play its protective role. Environmental allergens therefore easily penetrate the epidermis and cause an abnormal inflammatory reaction.

    Regarding psoriasis, 30% of cases correspond to familial forms involving genetic predispositions. The major gene involved is the PSORS1 locus. Other minor genes also play a role. The genetic variants associated with psoriasis are located in genes involved in immunity, which leads to a immune system imbalance causing chronic skin inflammation and an overproduction of keratinocytes.

    As previously discussed, these diseases are chronic inflammatory skin conditions caused by genetic predisposition. However, environmental factors also come into play: these are multifactorial diseases. The prevalence of eczema has increased in recent decades. It appears that environmental factors play a role in this increase. These could be theincrease in pollution, heightened hygiene levels, a greater presence of allergens (pets, dust mites), changes in dietary habits etc. However, it seems difficult to estimate the weight of these factors. As for psoriasis, the involvement of external factors is clearly established: medications, infections, mental stress, or lifestyle habits (alcohol, tobacco) can trigger or worsen psoriasis.

    Thus, eczema and psoriasis are both inflammatory diseases promoted by a genetic predisposition. External factors are also involved in their pathophysiology.

  • Non-communicable diseases.

    There are many misconceptions surrounding eczema and psoriasis, particularly the belief that they are contagious. This lack of understanding leads to the stigmatization of those affected, resulting in social isolation. It is important to know that these two conditions are not contagious. Indeed, they are of an inflammatory and non-infectious origin.

  • A psychological impact.

    Although the manifestations of these two dermatoses are primarily physical, they have a significant psychological impact. Indeed, like many chronic diseases, eczema and psoriasis can sometimes negatively affect quality of life, causing sleep disturbances, social withdrawal, irritability, and even depressive syndrome. This negative impact is due to the unsightly appearance of skin lesions, the itching they cause, and the stigmatization.

  • Eczema and psoriasis: these two conditions are not limited to just the skin.

    Contrary to what one might believe, psoriasis and atopic eczema are not confined solely to the skin. In the case of atopic eczema, this dermatosis is often associated with allergic rhinitis, food allergies and asthma attacks.

    In individuals with psoriasis, a quarter suffer from joint involvement, referred to as psoriatic arthritis. This condition is characterized by chronic inflammation of the joints, which swell and deform. Furthermore, certain diseases, particularly cardiovascular and metabolic diseases, are strongly linked to psoriasis. This includes hypertension, obesity, diabetes, and dyslipidemia.

How to differentiate between eczema and psoriasis?

  • A different age of onset.

    Traditionally, atopic dermatitis appears around 3 months of age and improves or even disappears by puberty.Psoriasis is a disease that primarily affects adults, with a peak onset between 20 and 40 years old. However, be aware that genuine cases of atopic eczema can begin in adulthood, and there are infants who suffer from psoriasis. Atopic eczema can persist into adulthood.

  • A differing localization of plaques.

    In babies, atopic eczema is primarily located on the face, the scalp , and the buttocks. Later, it can be found in the creases of the elbows, neck or knees (popliteal fossa), as well as on the hands and around the mouth.

    In regards to psoriasis, the lesions are located at the areas of friction, meaning the knees (patellas), the elbows, the navel, the loins, the buttocks and the lower back. They can also be observed at the level of the nails.

    There are areas such as the scalp or the auditory canals that can be affected in both diseases.

  • The appearance of patches: some differences.

    Eczema and psoriasis are both dermatoses characterized by the appearance of inflammatory red patches. However, they can be differentiated, as psoriasis patches are covered with thick, adherent whitish scales, which are very characteristic of this disease. Indeed, these result from a excessive proliferation of keratinocytes. Moreover, psoriasis patches are well defined.

    Eczema patches are ill-defined, erythematous patches that display vesicles. Most often, these vesicles rupture, leaving behind erosions that ooze, then become covered with crusts. Over time, scaling is observed. In cases of chronic eczema, the skin thickens: this is known as lichenification.

    Note : flakes can also be found on eczema lesions, particularly during the flaking phase. However, these are not characteristic of this disease and are less thick.


  • ORCHARD D. & al. Eczema management in school-aged children. Australian Family Physician (2017).

  • OHTSUKI M. & al. Risk factors for the development of psoriasis. International Journal of Molecular Sciences (2019).


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