Emergency doctors in Britain have issued a safety warning about water beads that can be given as gifts to children at Christmas.

Brightly colored soft plastic beads, also known as jelly balls, sensory beads or water crystals, are marketed as craft tools and household items – but also as toys.

They are usually only a few millimeters but can grow up to 400 times their original size in about 36 hours when exposed to some liquid, posing a hidden danger. If a child swallows it, it can cause bowel obstruction and the consequences can be fatal.

The Royal College of Emergency Medicine (RCEM) recommends that pearls should be kept away from children under five years of age.

The “safety flash” is for doctors to make sure they know what to look for while on duty, but the college also wants parents and caregivers to be alert to the dangers.

Pearls are not visible on X-ray.

They can cause suffocation and harm to children in the UK after reports have linked them to deaths overseas, government says The Office of Product Safety and Standards said in September.

It states that beads should only be used by older children or vulnerable adults under close supervision.

RCEM advises parents and caregivers to seek immediate medical attention if there is any suspicion that a child has swallowed a water particle.

RCEM vice-president Dr Salwa Malik told PA media: “After seeing the direct impact, which can be devastating and harmful, we are requesting people to please be aware of these dangers when choosing and giving gifts this season. “Think twice.” ,

The RCEM alert also highlights the potential danger to children and vulnerable adults from button or coin batteries and magnets if swallowed.