Invisible Ink Spy Pens
Spy pens with invisible ink were marketed as cool secret agent tools but contained toxic chemicals like formaldehyde. Children sometimes suffered chemical burns, especially when ink leaked or was rubbed into their eyes.
These hazardous “toys” were quickly banned after multiple injuries. While designed to encourage espionage play, the pens were far too dangerous for children, serving as a lesson in the importance of safe materials in toys.
