Obagi Professional-C Serum 20% - 0.42 fl oz

Yes, Obagi Professional C-Serum 20% is oil-free and non-comedogenic.

Vitamin C can cause temporary irritation and excess dryness if you have never used it before. For dry skin, we recommend beginning with Obagi Professional-C Serum 10% (http://www.lovelyskin.com/o/obagi-professional-c-serum-10) and gradually increasing to the 15% and 20% options as your skin grows more accustomed to this powerful ingredient.

Yes, Obagi Professional-C Serum 20% does not contain hydroquinone.

Obagi Professional-C Serum 20% does not have an expiration date listed on its packaging, however we receive frequent shipments of this product directly from the manufacturer so we always have the freshest stock on hand. Vitamin C serums like this one have a two-year shelf life unopened, and once you open it you should use the product within 6-9 months for optimal benefit.

The pH of Obagi Professional-C Serum 20% is 2.0 - 2.4.

When introducing Obagi Professional-C Serum 20% into your Obagi Nu-Derm routine, we recommend applying it as the first treatment step in your routine both morning and evening, right after cleansing and toning your skin. You can then follow with Clear #3 and the rest of your Nu-Derm regimen. We hope this information helps!

You can use Obagi Professional-C Serum 20% in the evening along with your tretinoin cream. You should apply the Obagi Professional-C Serum first (right after cleansing and toning), followed by the blender and tretinoin (you would mix these two together and apply in one step). We hope this information helps!

Obagi Professional-C Serum 20% can range in color from clear to straw yellow, and after opening gradually turns a darker yellow to orange color over time. This change in color does not affect the product's efficacy. You should store your Obagi Professional-C Serum at room temperature and away from direct sunlight. We hope this information helps!

Yes, because of its potency, it can take a while for your skin to become acclimated to vitamin C. If you have not used a vitamin C serum before, we suggest starting with the Obagi Professional-C Serum 10% (http://www.lovelyskin.com/o/obagi-professional-c-serum-10). This serum contains 10% L-ascorbic acid to brighten your complexion while increasing collagen production. Once your skin is acclimated to this concentration of Vitamin C (usually after you use one bottle), then you can start using the Obagi Professional-C Serum 15%, followed by the Obagi Professional-C Serum 20%. We recommend using this product in the morning for antioxidant protection during the day, and you can also use it during your evening routine.

Most antioxidant serums, including the Obagi Professional-C Serum, are best used in the morning, so they can best defend against environmental damage during the day. That said, there are no negative effects to using this serum at night.

The Obagi Professional-C Serum is primarily for reducing the look of wrinkles, fine lines and other signs of photoaging.

In general, cosmetic products have an expected shelf life of twelve to thirty-six months. We recommend using the Obagi Professional-C Serum within a year of opening the bottle.