Foam mattresses absorb 46% more moisture than any other type of mattress, according to bed maker Harrison Spinks.
Moist mattresses are “a breeding ground” for bacteria, the firm said.
Bacteria that reside in mattresses include Staphylococci, Enterococci and even the deadly MRSA superbug.
Infections from the bacteria can cause painful lumps on the skin, cellulitis, collections of pus under the skin, pneumonia and urinary tract infections.
Harrison Spinks head of research Melissa Cockerill said: “While foam mattresses may be comfortable, they don’t offer the best sleeping environment when it comes to moisture evaporation and breathability.
“Foam is good for absorbing the moisture lost while we sleep, but isn’t as effective at evaporating this moisture, meaning it is often stored at the mattress’s core – the ideal breeding ground for bacteria.”
The average person sweats almost enough to fill a 330ml can of fizzy drink every night.
Air doesn’t flow through foam mattresses as effectively as other types, so not as much moisture is evaporated.
The best type of mattress to avoid unwanted, hidden bacteria was those using natural fillings, Harrison Spinks said.
Wool or cotton mattresses were fresher and dryer, because air flow was more efficient in the mattress.
About 23% more moisture was evaporated in wool mattresses than foam ones, the bed maker added.
So, less dust mites and bacteria would reside within natural mattresses.
“Those looking to keep their mattress fresh should look for a mattress boasting a host of natural fillings,” said Cockerill.
“There’s a misconception that the fibrous nature of natural mattress fillings mean they’ll house more bacteria, but this isn’t the case.
“Fillings such as the home-grown wool, cotton and flax we use offer much better absorption and wicking properties.”
It was estimated that a 10-year old mattress could hold more than 10lb in dead skin.