According to US health officials, these spooky lenses - which are illegal under federal law but are commonly sold at retail outlets or online - can cause eye infections, conjunctivitis and impaired vision.
Contact lenses are classified to be medical devices in the US. The FDA advises instead asking a doctor or an optician for a prescription for decorative lenses rather than buying them over the counter or online, making sure a proper eye exam is given to ensure they fit correctly.
Similar health concerns about the use of these lenses are being raised in Jersey, where it's reported that at least three people have suffered eye problems after using them last year.
In the UK, contact lenses should also only be given out via a prescription.