Some mattress protectors are waterproof.
Mattress protectors that are designed with a plastic waterproof underside will fully prevent any liquids from penetrating the mattress.
Our favourite waterproof mattress protector reviews:
Nectar mattress protector review
DreamCloud mattress protector review
Emma mattress protector review
But some mattress protectors, such as the Simba mattress protector, are only water resistant.
This means the protector is able to resist some penetration of water, but some will still leak through.
You should check with the manufacturer and on the product page to see if the mattress protector is waterproof.
Our article has a list of the best waterproof mattress protector UK brands.