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Objectives: The goal of the study was to assess microscopic differences in inflammatory response and neocollagenesis with varying concentrations of croton oil delivered via topical cotton-tipped applicator. Introduction: Deep chemical peels consist of a mixture of croton oil, phenol, and water. Depth of penetration of deep chemical peels is variable, depending on the concentration of the chemical agent (i.e. phenol and/or croton oil) used. Materials / method: Using a porcine animal model, varying concentrations of croton oil (0.8% and 2.4%) were applied to the skin via cotton-tipped applicator. The degree of neutrophilic inflammation (characterized by netosis band and measured by neutrophil count) and neocollagenesis (measured by collagen III band thickness) were evaluated in hematoxylin and eosin-stained (H&E) punch biopsies performed 24 hours and 21 days after chemical peel application, respectively. Herovici collagen stain was used to differentiate between new type III collagen production and mature type I collagen on day 21. Results: Non-parametric testing was performed to compare the 0.8% and 2.4% croton oil concentrations. Median collagen type III band thickness was 117.5 micrometers for the 0.8% concentration and 151.1 micrometers for the 2.4% concentration as shown by Herovici collagen staining 21 days post-procedure. H&E staining at 24 hours revealed a median depth of injury of 1401 micrometers for the 0.8% croton oil concentration and 1274 micrometers for 2.4% croton oil concentration. All results were statistically significant. Conclusion: Despite more superficial depth of injury, use of 2.4% croton oil led to a thicker collagen type III band. Higher concentrations (greater than 1.6%) of croton oil might interfere with phenolic coagulation and depth of injury, but not with neocollagenesis. Previous research had suggested deeper depth of injury and more necollagenesis with the 1.6% than the 0.8% and 2.4% concentrations, suggesting that the effect of croton oil likely plateaus at a concentration of around 1.2-1.6%. Future studies using human subjects are needed to assess optimal croton oil concentration to use in chemical peels.