The U.S. Food and Drug Administration warned CVS, Walgreens and other companies that they violated federal law by marketing unapproved eye products.

The eye products are being illegally marketed as being able to treat cataracts, glaucoma, conjunctivitis and more. The FDA said some of the eye products are labeled to contain silver and long-term use can cause skin and body tissues, including the eye, to permanently turn gray or blue-gray.

The companies have 15 days to respond to the FDA’s warning letter as it continues its investigation.