Skinceuticals c 10 serum skin staining issue.

It is quite unusual for Serum 10 to stain your skin, you may be applying too many drops and not allowing the product to sink in before applying your other skin care steps. 
Try applying a drop on each area of your face and gently pat, allow to sink for 2-3 minutes before applying any other products. You can even try leaving the product on for half an hour for maximum absorption and see if this helps. 

Thank you for sharing your concern. Please allow the product to absorb before applying other skincare products.
SkinCeuticals Serum 10 should not be staining the skin. Are you applying this over the face or doing a spot treatment? It is also recommended to apply a broad spectrum sunscreen, like SkinCeuticals Physical Fusion UV Defense SPF50 after Serum 10. We would like to speak with you regarding your experience. For further assistance, please give us a call at 1-877-998-0196, Monday-Thursday between 8:30 am and 5:30 pm CST, Friday between 8:30 am and 5:00 pm CST, and one of our Consumer Advocates will be able to assist. Looking forward to hearing from you.