Seborrheic Dermatitis or Psoriasis: How to Tell the Difference?

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

• The seborrheic dermatitis (seborrheic dermatitis): This skin condition is an inflammatory dermatosis characterized by the appearance of erythematous red patches with oily scales. The lesions it causes are primarily located in areas rich in sebaceous glands. They affect the groove between the cheeks and the nose, the scalp, or even the eyebrows and the eyebrow arch.

  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 appear in patients with genetic predispositions. It can also occur 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.
  The worsening of psoriasis, in 20 to 25% of cases, can 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 that are more pronounced than those of psoriasis.

• Psoriasis does not typically come with significant itching, although this can intensify in some patients. Occasionally, a person 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 recognition 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).