Obagi Obagi-C Rx System C-Clarifying Serum 1oz, 30ml Obagi Obagi-C Rx System C-Clarifying Serum has the following features:Contains the antioxidant Vitamin C and prescription-strength hydroquinone.This patented formulation for normal to dry skin reduces the appearance of dark spots for a lighter, brighter complexion.CAUTIONS : Obagi-C Rx System C-Clarifying Serum contain Sodium Metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life threatening or less severe asthmatic episodes in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than nonasthmatic people. Only a thin application should be applied. If no improvement is seen after 8 to 12 weeks, use of product should be discontinued. Hydroquinone (HQ) and Tretinoin / Retinol products should not be used by pregnant women, women who intend to become pregnant in the near future, or women who are lactating/breast feeding. Test for skin sensitivity before using by applying a small amount to an unbroken patch of skin and check within 24 hours. Minor redness is not a contraindication, but where there is itching or vesicle formation or excessive inflammatory response, product should be discontinued and physician consulted. Close supervision is recommended. Sunscreen use is an essential aspect of HQ therapy because even minimal sunlight exposure sustains melanocytic activity. Avoid contact with eyes, nose, mouth, or lips. In case of accidental contact, rinse eyes, nose, mouth, or lips with water and contact physician.