What is the “purging phase” after skincare and how can it be distinguished from an “allergic reaction”?

Purging, particularly after treatments involving salicylic acid, retinol, or deep pore cleansing, accelerates the skin’s cell turnover, causing plugs and pimples that were already forming beneath the skin to be simultaneously propelled to the surface. During the purging phase, pimples only appear in areas where the person “always gets pimples” and disappear without a trace within 2-3 weeks; this indicates that the treatment is working. In case of an allergic reaction, intense itching, burning, small fluid-filled blisters, or widespread hives-like redness occur immediately after the treatment all over the face (including cheeks and eye area where pimples never appear). Allergy requires immediate medical attention.