Keratolytics for treating psoriasis?

Psoriasis plaques are characterized by significant hyperkeratosis in the corneal layer. It is necessary to first remove this dry and hard area, which highlights the importance of keratolytic treatments. As the name suggests, keratolytic treatments have the ability to soften the skin's keratin and promote the removal of skin crusts. These treatments are particularly recommended for thick plaques.

Urea,salicylic acid,lactic acid,and glycolic acid are the primary components of keratolytic treatments. They exhibit exfoliating and keratolytic actions, which help to soften skin roughness. However, salicylic acid is the most commonly used. Indeed, it works by interfering with the intercorneocyte space in the stratum corneum through the inhibition of cholesterol sulfotransferase. This enzyme converts cholesterol into cholesterol sulfate, a hydrophobic molecule, allowing it to cross the plasma membrane and reach the intercorneocyte space. By inhibiting this, it promotes the detachment of dead cells. In addition to its keratolytic power, this molecule also has astringent effects, thus stimulating skin renewal.

Good to know: Keratolytic treatments are beneficial before the application of other topical medications, as they facilitate their absorption. They can be used alone or in combination with a dermocorticoid. In this case, the action of the keratolytic enhances the absorption process of the dermocorticoids at the level of the epidermis.

Salicylic acid is typically used in masterful preparations such as salicylic oil, salicylic vaseline, or salicylic cream on targeted areas. The duration of the treatment varies depending on the size and location of the hyperkeratosis. A daily application of the salicylic product at 5 or 10% is prescribed for a duration of one week, followed by a biweekly or triweekly renewal.

The primary issue with the topical treatment of psoriasis using salicylic acid is the potential for systemic toxicity, either chronic or acute, accompanied by symptoms such as burning of the oral mucosa, headaches, or vomiting. Other adverse effects related to salicylic acid primarily include irritations in cases of high concentration or allergies in certain patients. These symptoms can occur during the topical treatment of large body surfaces. Therefore, salicylic acid should not be applied to more than 20% of the body surface. The application on large surfaces requires particular monitoring by a healthcare professional.

Keratolytic treatments should not be applied to sensitive areas of the body, including the eyes, mucous membranes, or genital areas. If used in conjunction with dermocorticoids, space out the application as salicylic acid promotes the absorption of these into the bloodstream with prolonged use. The cessation of treatment should be done gradually. Ideally, applications should be spaced out, a less potent corticoid should be used, or alternated with a preparation without a dermocorticoid.

Keratolytic treatments are not intended for everyone due to certain contraindications.

• Association with other psoriasis treatments.

  The combination of keratolytic treatments with dermocorticoids promotes the passage of corticoids into the bloodstream. Therefore, it is necessary to space out the applications. Moreover, some studies have shown that keratolytic treatments, particularly salicylic acid, deactivate treatments based on calcipotriol, although there are no clear explanations for this. Therefore, it is not recommended to combine them together.

• Use of other keratolytic agents.

  The use of salicylic acid in conjunction with other keratolytic acids such as glycolic acid and azelaic acid is not recommended as this combination can promote excessive exfoliation of the epidermis.

• Widespread Psoriasis.

  The use of keratolytic agents should not exceed more than 20% of the body surface area as it could potentially cause systemic toxicity or other significant side effects.

There are other contraindications to the use of keratolytic treatments such as ulcerated lesions, primary bacterial or fungal infections. Generally, consult with your dermatologist to determine whether or not the use of keratolytic treatments is appropriate for you.

• BASHIR S. J. & al. Cutaneous bioassay of salicylic acid as a keratolytic. International Journal of Pharmaceutics 292 (2005).

• FLUHR J. W. & al. Emollients, moisturizers, and keratolytic agents in psoriasis. Clinics in Dermatology (2008).

• THIELEN A-M. Traitements topiques du psoriasis en 2009. Revue Médicale Suisse (2009).