Toner Formulation with Urea and Salicylic Acid

Yes, it is possible to prepare a liquid toner formulation containing 8-10% Urea and 2% Salicylic Acid. To achieve a clear, liquid product suitable for patting onto the skin, it is crucial to use a water-soluble form of Salicylic Acid.

For the Salicylic Acid component, a water-soluble option like ActiveRelease™ Salicylic Acid (Powder, Water-Soluble) is suitable, as it can be dissolved directly in water and is formulated to deliver 2% pure Salicylic Acid at a 5% usage rate, which aligns with the desired concentration and FDA regulations for leave-on products.

Urea (High Purity, Cosmetics, Powder) can be used at the requested 8-10% concentration, which provides both moisturizing and mild exfoliating benefits.

Limitations and Stabilization of Urea

Beyond general stabilization needs, Urea has specific limitations:

• Heat Sensitivity: Urea is sensitive to heat and can disintegrate more quickly at temperatures above 35°C. Higher temperatures make Urea less stable.
• pH Instability: When dissolved, Urea can cause the pH of the formulation to become more alkaline over time. If not controlled, the pH can rise significantly.

To stabilize Urea and maintain the desired pH (ideally in the range of 4-5.5, which also benefits Salicylic Acid's efficacy), stabilization techniques are necessary for products intended for long-term storage or exposure to temperatures above 30°C. Methods include using:

• Gluconolactone: At approximately 15% of the Urea concentration (e.g., 1.5% Gluconolactone for 10% Urea).
• Triacetin: At a ratio of approximately 1 part Triacetin to 10 parts Urea.

Controlling the pH with these or other acidic components is key to preventing the pH from rising and ensuring Urea's stability.