Is "purging" a real thing?

The claim

When starting a retinoid or acid, skin gets worse before it gets better as congestion is pushed to the surface. This is "purging" and you should continue through it.

What the evidence actually shows

A review in the Journal of Drugs in Dermatology examined the available clinical trial data and found no primary trial evidence supporting the dogma of retinoid-induced acne worsening. Available data showed improvement even during the first weeks, and the authors concluded that any early worsening reflects the natural course of the disease rather than the retinoid.

A second analysis, of lesion-count data from trials of a clindamycin and tretinoin gel, likewise found no evidence of flaring. A small excess of patients with a 10% or greater increase in inflammatory lesions appeared only in the mildest-acne subgroup — 15.4% against 8.7% on vehicle — which is a weak signal in the group with least room to improve.

So the phenomenon is not established. Which does not mean nothing happens when people start retinoids: irritation, dryness, erythema and flaking are real, common, dose-dependent and well documented. Those are irritant effects with a known mechanism.

Why this matters practically

The purging concept is not harmless, because it supplies a reason to continue through any adverse reaction. Irritant dermatitis, an acneiform eruption or a genuine allergic response all look like "getting worse before better", and the framework tells you to persist. Since there is no validated way to distinguish purging from an adverse reaction — because purging has no validated existence — the safer reading is to treat worsening as what it appears to be.

A sensible rule: transient dryness and mild flaking while building tolerance is expected. Increasing inflammation, pustules, burning or spreading redness is a reaction, and the response is to reduce frequency or stop, not to push on.

What to do instead

Build up slowly — twice weekly, then more often. Apply to dry skin, buffer with moisturiser, support the barrier. Expect months for benefit, and treat a genuine flare as information rather than progress.