Sulfur + retinoid
Keep them apartKeep them apart. Retinoid labels specifically flag sulfur as a concomitant irritant - stacked with a retinoid it compounds dryness, redness and peeling.
Both are legitimate acne tools, so alternate instead of stacking: sulfur one night, retinoid the next, or sulfur in the morning and the retinoid at night. Sulfur spot treatments on different areas from your retinoid zones also work.
Buffer either way: moisturizer after actives, or before them on sensitive skin - cushioning doesn't cancel the active.
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