Seborrheic Dermatitis or Psoriasis: How to Tell the Difference?

To understand the difference between seborrheic dermatitis and psoriasis, it is appropriate to take a comprehensive look at the characteristics of these two diseases.

• The seborrheic dermatitis (seborrheic dermite): This skin condition is an inflammatory dermatosis characterised by the appearance of erythematous red patches with oily scales. The lesions it causes are primarily located in areas rich in sebaceous glands. These include the groove between the cheeks and the nose, the scalp, and even the eyebrows and the brow ridge.

  Seborrheic dermatitis is not contagious. It is a benign disease, but it can progress in recurrent flare-ups. This skin issue impacts patients' lives due to its visibly apparent lesions. The onset of the seborrheic dermatitis can be due to the proliferation of Malassezia type fungi or an overactivity of the sebaceous glands. Genetic predispositions are also sometimes responsible.

• The psoriasis: This is a chronic inflammatory disease primarily affecting the skin and joints. It can occur in patients with genetic predispositions. It can also arise due to climate variations, local traumas, psychological stress, the intake of certain medications or other factors. This chronic inflammatory skin disease develops in flare-ups of red patches with scales.

  Even though psoriasis is benign, it impacts the quality of life of patients. Psoriasis can begin at any age, even in infants. The average onset age is estimated to be 33 years, with 75% of cases starting before the age of 46.
  In 20 to 25% of cases, the worsening of psoriasis may be accompanied by joint pain or due to extensive skin damage. This is referred to as psoriatic arthritis.

Some symptoms related to seborrheic dermatitis or psoriasis can be confusing. However, there are a few distinguishing factors between the two diseases, such as the appearance of the lesions.

• Seborrheic dermatitis presents with patches covered in yellow, oily scales, which are more pronounced than those seen in psoriasis.

• Psoriasis is not typically associated with significant itching, although this can intensify in some patients. Occasionally, an individual may exhibit seborrheic dermatitis on the face and psoriasis on the body. This is referred to as psoriasis of the seborrheic regions.

• Damage to the joints (elbows, knees) and potentially joint pain due to psoriatic arthritis will facilitate the identification of psoriasis.

• Microvascular changes are observed in individuals affected by psoriasis and are detected in a minority of people suffering from seborrheic dermatitis.

• ROSINA P. & al. Videocapillaroscopy in the differential diagnosis between psoriasis and seborrheic dermatitis of the scalp. Dermatology (2006).

• SAURAT J. & al. Dermatologie et infections sexuellement transmissibles (2016).