RALEIGH, N.C. (WNCN) – Warning letters from the Food and Drug Administration (FDA) were sent out on Tuesday to eight companies, including CVS and Walgreens, for marketing unapproved eye drops.

The letters claim some eye care products that have been marketed and sold to treat things such as conjunctivitis, glaucoma, cataracts and pink eye have not been approved by the FDA.

The FDA said the eye products were labeled to contain silver, and long-term use of drugs containing silver could result in parts of the skin, including in the eye, permanently turning gray or blue-gray hue, which is a condition called argyria

On Tuesday, CVS stopped “Pink Eye Relief Eye Drops” from being sold. People who bought the product can return the purchase for a refund.

Companies who received a letter from the FDA have been asked by the U.S. health regulator to respond with how they will correct the violations within 15 days of receiving the letters.