An expert has warned people not to jump straight into the shower after returning home from holiday.
Microbiologist Dr Tom Makin, from Cheshire, has advised that you run the shower for at least 20 minutes - and it could save your life.
He said the danger of exposing yourself to toxic bacteria, legionella, via stagnant water increases after spending a long period of time away from home.
Speaking to the Mail on Sunday , Dr Makin said: "I cover my nose and mouth with one hand and turn on the shower with the other.
"After 20 minutes or so, I’ll turn the shower off and then I won’t go back into the bathroom for at least another 20 minutes."
Inhaling legionella can cause the life-threatening condition legionnaire's disease - a form of severe pneumonia.
It is a bacteria that thrives in stagnant water above 20C and below 45C - and inside your shower head is the perfect breeding ground.
The chance of the toxic bug being inhaled increases during the warm summer months and will be higher if you have been on vacation for a few days, giving the microbe chance to multiply.
Official figures show around 500 people in the UK are infected with legionella every year, and the World Health Organisation says an increase worldwide could be attributed to people having more showers than baths.
