When to Stop a Peel and What Frosting Tells You
Chemical peels remain a trusted tool in aesthetic clinics for refreshing the skin. One of the most important signs practitioners watch for during these procedures is a visual cue called frosting. This distinctive whitening of the skin isn’t just a surface change; it reveals the depth of the peel and how the skin is responding to the acid.
Frosting appears when peeling agents denature proteins in the skin. Trichloroacetic acid (TCA), for instance, causes keratocoagulation. As the proteins lose their natural structure, they scatter light and turn white, similar to how egg whites cook. This visible reaction tells you how far the acid has penetrated. In contrast, some agents, like salicylic acid, create what’s called pseudo-frosting. That’s not due to skin injury, but to crystallisation as the peel dries.
Professionals group frosting into three levels. First, there’s a light, patchy haze often seen with lower-strength acids or after one pass of product. This is superficial and may cause mild flaking. Second, there’s uniform frosting with pink undertones; this suggests a medium-depth peel. Last, there’s dense, solid white frosting, often achieved with multiple layers or stronger acids. This signals deeper skin injury, with more downtime and greater risk.
TCA is the most predictable acid for achieving true frosting. Low concentrations around 10 to 15 percent might only produce a light haze, but 20 to 35 percent applied in layers can give consistent, even frosting. Salicylic acid, on the other hand, forms a superficial white coat that disappears when wiped. With Jessner’s solution-a mix of lactic, salicylic acid and resorcinol-you get a gradual frosting effect that builds with layering.
Glycolic acid doesn’t frost. You rely on skin colour changes and timing instead. And phenol, used rarely now, creates a greyish-white frost linked to deep tissue injury. It’s powerful, but comes with systemic risks, so it’s used sparingly.
Reading frost correctly is essential for safety and outcomes. It’s your visual endpoint. When TCA starts to frost, you stop. Pushing past that moment increases the risk of burns or scarring. If the frosting appears uneven, it may be due to differences in skin thickness, residual oil, or inconsistent application. Always assess the full picture.
In darker skin tones, frosting may be harder to see. This can lead to accidental overtreatment, so it’s vital to work conservatively and pre-condition the skin with agents like retinoids or pigment suppressors. If you’re unsure about depth, err on the side of caution.
Grey, yellow or brown tones in the frosting aren’t good signs. These colours might suggest thermal injury or product pooling. Frost that appears too quickly, or with clear streaks or drip marks, needs immediate attention. It’s always better to under-peel and re-treat later than to chase results in one sitting.
To guide the process effectively:
Watch carefully as the peel develops.
Understand which acids produce true versus pseudo-frosting.
Adjust for different skin types and areas of the face.
Educate clients on what frosting means and what they can expect during healing.
Being able to read and control frosting lets you use chemical peels more confidently. You’ll understand how to stop at the right moment, tailor your approach to each client, and avoid complications. It’s not just about seeing white on the skin; it’s about knowing what that white means.
With practice, you’ll spot the difference between safe frosting and signs of trouble, and you’ll be able to deliver strong results with minimal risk. That’s where clinical skill meets chemical precision, and why frosting is a key marker every aesthetic professional should master.
