With Halloween on the rise, so are decorative contact lenses. These are contact lenses meant to only change only the color or design of your eyes, but keeping your vision the same.

Decorative contact lenses come in all sorts of colors and designs—from glowing purple to dark black. People use these for all sorts of costumes—whether you want to be a cat and have eyes with a yellow tint, a vampire with blood red eyes, or a witch with glowing green peepers.

While decorative contacts can be aesthetically pleasing, and give the finishing touches to a great costume, there are a few risks that the FDA wants users to know about. They recently issued a report about the risks you take when you put these colorful lenses in your eyes—plus the importance of buying legit ones.

Just like regular contact lenses, decorative contacts can damage your eyes in more ways than one, especially if used incorrectly. Just some of the harm they can cause include:

• Getting a corneal abrasion (a cut or scratch on the top layer of your eye)
• Allergic reactions including itchy, watery red eyes
• Blurry or decreased vision
• Painful eye infection

Take the decorative lenses out immediately if you experience any of the following symptoms:

• Redness
• Swelling
• Stinging
• Feeling as if there’s sand in your eye
• Dull or sharp pain in your eye
• Discharge coming from the eye
• Seeing double or blurry vision

If any of these issues persist, give your optometrist or ophthalmologist a call to schedule an appointment for a check-up. While rare, it’s still possible that an eye infection could cause you to become blind if it isn’t treated right away.

“Most people believe that decorative lenses do not require the same level of care or consideration as a standard contact lens because they can be purchased over-the-counter or on the Internet,” says Thomas Steinemann, MD, professor of ophthalmology at Case Western Reserve University in Cleveland. “This is far from the truth.”

Part of the problem is knowing where to buy decorative contact lenses from. Most people don’t know that decorative contacts are medical devices. You can buy decorative contact lenses from your eye doctor or online from a mail-order company, but it’s important that it’s a company that sells FDA-cleared or FDA-approved contact lenses and always requires you to provide a prescription. Any retailers selling these without a prescription are breaking the law and aren’t legit.

“Many of the lenses found online or in beauty salons, novelty shops or in pop-up Halloween stores are not FDA-approved and are being sold illegally,” Dr. Steinemann said. Retailers that sell contacts without a prescription are breaking the law and could be fined for each violation.

Thus, you still need to get a prescription for decorative contact lenses, even if they aren’t altering your vision. Be sure to ask them for that before you purchase.

That said, don’t share your contact lenses with anyone else, and vice versa, don’t borrow your lenses from a friend. Everyone’s eyes are different, and so are contacts (which are made to fit your eyes).

Additionally, always follow cleaning and disinfecting procedures in the directions your contact lenses come with.

Have you ever worn decorative contact lenses? Do you plan to get a prescription from your eye doctor to get a pair for a Halloween costume?