With Halloween approaching, United Kingdom eye experts issued warnings about the risks of improperly wearing novelty contact lenses, reporting they can cause eye scratches and infections.

The Association of Optometrists, an organization representing over 30,000 optometrists in the U.K., said around Halloween many of its members treat patients for eye-related complications resulting from novelty contact lenses. Many people use cosmetic lenses as part of their Halloween costumes, and optometrists warned against wearing lenses that have not been approved by professionals.

“Each year we treat patients, including children under 16, who have developed eye conditions after wearing cosmetic contact lenses,” Bardul Hussain, consultant ophthalmic surgeon at Moorfields eye hospital, said to various media outlets. “Not knowing the basics of using contact lenses safely can put you at higher risk of developing painful eye injuries, infections and, in the worst cases, risk of permanent sight loss.”

cosmetic contact lenses A fan with colored contact lenses poses for a picture at 2014 New York Comic Con (October 10, 2015). UK eye experts are warning against cosmetic contact usage, saying if illegal pairs are worn, they could cause permanent eye damage. Photo: Mike Coppola/Getty Images

Hussain also said patients share lenses with others, wear the same pair past the expiration date and store them in tap water. These actions can result in eye injuries and possible permanent sight loss. The cornea, a delicate, clear area at the front of the eye, can be scratched by shoddy novelty contact lenses.  

Optometrists said cosmetic contact lenses should only be worn if sold by a registered optician or a qualified doctor. However, many people buy cheap lenses online and in person. These lenses are known as zero-powered lenses because they do nothing to correct the wearer’s eyesight. An Omnibus survey reported 7 percent of the general U.K. public has worn zero-powered contact lenses, but 21 percent of that figure exists among 25-34-year olds.

Optometrists suggested the following for safe cosmetic contact lens use:

  • Have a medical eye professional check if the lenses fit safely
  • Keep the lenses clean with contact lens solution
  • Do not let the lenses come into contact with water
  • Do not wear the lenses all night
  • Do not share the lenses with other
  • Buy and sell the lenses under the supervision of a registered professional, it is illegal not to

Vicky McDermott, chief executive of the General Optical Council, a body responsible for upholding optometrist regulations in the U.K., said when worn safely, the risk of wearing cosmetic contact lenses is low. However, if illegal lenses are procured, wearers are putting lenses in their eyes that have not undergone the safety checks necessary to make them safe for use.