When first using No. 9 do a patch test on wrist to see if irritation occurs. Wait at least an hour and examine skin for redness or irritation. If irritation occurs discontinue use and consult a doctor. Not suitable for those under 18 years of age. Do not use with burned, irritated, or medicated skin. Do not use in conjunction with retinoic treatment or Vitamin C serums. External use only. Do not apply immediately after shaving. Wait at least 4 hours after shaving to apply No. 9 to avoid irritation. May increase sun sensitivity, avoid immediate and unprotected sun exposure. Wear sunscreen when using this product. Avoid contact with eyes and eye creases. If contact with eyes occurs, flush with plenty of water for several minutes and consult a medical care professional. Skin Purging may occur when first using the No. 9 Chemical Exfoliant. For more info, click here . If necessary, discontinue use of No. 9 and consult a medical professional.