Wearing funky-coloured contact lenses with your scary halloween outfit is unlikely to cause any lasting damage, if they were bought at registered opticians or doctors.
But, more than half of people admitted buying cosmetic contact lenses from joke shops or over the internet, a survey revealed.
Without important safety checks and advice given by opticians when buying the lenses, the public risks serious damage to their eyes, according to the General Optical Council.
Partygoers were urged to not let other people try on their lenses, and to always wash hands before touching their eyes.
“When worn safely, the risks associated with cosmetic contact lenses are low,” said the General Optical Council’s Chief Executive, Vicky McDermott.
“However, when lenses are sold illegally, wearers are denied important safety checks and advice, putting them at risk of serious damage to their eyes.
“Party-goers can better protect their sight by buying their lenses from a qualified professional.”
Eye specialists advised the public to not sleep in their contact lenses, and to never let the lenses come into contact with water.
Doctors reported a spike in the number of people admitted to A&E around Halloween.
Eye damage from cosmetic contact lenses, was one of the reasons for the rise in patients, they said.
Consultant Ophthalmic Surgeon at Moorfields Eye Hospital, Badrul Hussain, said: “Each year we treat patients, including children under 16, who have developed eye conditions after wearing cosmetic contact lenses.
“There can be an increase in these problems in the period around Halloween. Some of the cases we see, like patients sharing lenses with friends, wearing the same pair year after year well past the expiry date, and storing them in tap water, have devastating effects.
“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.
“The cornea, the clear window at the front of the eye, is delicate and can be scratched easily by inexperienced contact lens wearers.
“This can expose the eye to organisms that can cause nasty infections, which in extreme cases can result in permanently impaired, or loss of, vision.”
By law, cosmetic contact lenses shoulkd only be sold under the supervision of registered opticians or doctors.