Public bogs almost invariably feature electric hot air hand-dryers, which are generally assumed to be more hygienic than other hand-drying methods. But this is not true.

Research has shown that paper towels win hands down (as it were): they dry your hands more quickly, they remove more bacteria and they are less likely to lead to cross-contamination. The hospitals I have found myself visiting recently seem to acknowledge these research findings because paper towels are the norm in their loos. Unfortunately, most other bogs accessible to the public do not offer this hygienic choice.

The popular idea that hot air dryers are more hygienic seems to be just a marketing ploy. These machines are presumably attractive to loo providers because their installation means not having to make arrangements for replenishing stocks of clean towels and disposing of soiled towels.

So what are the facts?

  • Speed of drying Research suggests that 10 seconds of drying with a paper towel is as effective as at least 40 seconds using a standard hot air hand dryer. Jet air dryers, however, dry your hands as quickly as paper towels.
  • Removing bacteria Although a hot air machine will dry your hands, it will not remove many of the bacteria that have survived the washing process. One study found that paper towels reduce the number of all types of bacteria but hot air dryers somehow increase their number, while jet air dryers increase the number of some but not all. Another study found that rubbing the hands together under a hot air dryer actually prevents the removal of bacteria and leaves you with more bacteria on your hands than if you had not used the dryer at all. This study also found that 10 seconds under a jet air dryer was more effective at removing bacteria than 30 seconds using a normal hot air dryer. However, using a paper towel was easily the best method of removing bacteria, especially from the fingertips.
  • Cross-contamination Because a hot air hand dryer take so long to get your hands completely dry, you may well leave the bog with your paws still a little damp. Since bacteria are more likely to be passed from wet skin than from dry skin, this increases the risk of spreading infection. In environments where people may be vulnerable to infection, such as hospitals, thorough attention to hand drying could therefore save lives. Studies have also shown that, unlike towels, hot air hand dryers disperse bacteria into the air, thereby putting other bog-users at risk. A typical hot air dryer can spread bacteria up to a metre (that’s more than three feet, for American readers), while jet air dryers can spread them up to two metres (six feet).

The most important thing to remember is that, whatever facilities may be provided, you should both wash and dry your hands as thoroughly as possible before going on your way.