Are Glow‑in‑the‑Dark Products Safe? The Science, History, and Simple Safety Tips

Glow‑in‑the‑dark stickers, pajamas and paints have been a nostalgic part of many childhoods — and they’re still popular in home décor and novelty items today. Their soft, lingering glow is charming, but it raises a reasonable question: what makes them light up, and are they safe?

How modern glow materials work

Certain minerals phosphoresce: they absorb light energy and then release it slowly as visible light when placed in the dark. Two common modern pigments are zinc sulfide treated with copper and strontium aluminate doped with europium. Light excites electrons in these materials; as the electrons return to lower energy states, they emit the familiar glow.

"When [an electron] returns home, it gives off a glow," explains Dean Campbell, a chemistry professor at Bradley University.

Strontium aluminate formulations generally produce a brighter, longer‑lasting afterglow than zinc sulfide, which is why many newer products use it. The glowing effect fades over time once the light source is removed, so items need periodic recharging by exposure to light.

A dark chapter: radium and the "radium girls"

Not all luminous materials have been safe. In the early 20th century, manufacturers mixed radium — a radioactive element — with phosphors to make paint that glowed continuously. Workers who painted watch dials and other objects were often told the paint was harmless and sometimes licked their brushes to shape them. Repeated radium exposure caused devastating radiation injuries and cancers in many workers; these tragedies led to stronger safety rules and the end of radium use in consumer luminous paints.

Are today’s glow products safe?

Modern phosphorescent pigments such as copper‑doped zinc sulfide and europium‑doped strontium aluminate are not radioactive and do not carry the same hazards as historical radium paints. For most users, glow‑in‑the‑dark stickers, textiles and novelty items are no more dangerous than other everyday consumer goods.

That said, these products are not food. Avoid intentionally licking or ingesting glow pigments, stickers or paints. As with any non‑food item, keep them away from very young children and pets who might chew or swallow small pieces. If you’re using glow paint in a craft project, follow the manufacturer's instructions, work in a well‑ventilated area, and avoid sanding or creating dust from dried pigments.

Practical tips

• Buy products from reputable manufacturers and check toy safety labels for age recommendations.
• Supervise young children when they use stickers or glow toys and keep small items out of reach.
• If using glow paints, read the safety data sheet or label, wear gloves if recommended, and avoid inhaling dust or fumes.
• If you find an unlabeled vintage luminous item (for example, an antique watch), treat it with caution and consider having it tested if you suspect it may contain old radioactive materials.

Enjoy glow‑in‑the‑dark products as intended — stuck to a ceiling, dotting a bedroom wall, or accenting a costume — and they’ll add a bit of wonder without significant risk when used responsibly.