Hands should be washed for a full 20 seconds, but the water doesn't have to be hot. (Mary Altaffer/AP Photo)

Most people don't wash their hands often or thoroughly enough after using the bathroom, a British study of commuters showed.

Researchers have found bacteria on hands in hospitals, but few have looked at the hands of the general population.

"The results were quite shocking," said study author Gaby Judah of the department of infectious and tropical diseases at the London School of Hygiene and Tropical Medicine.

Judah and her colleagues sampled commuters' hands in various cities in the U.K. Overall, more than 25 per cent had fecal bacteria on their hands, the researchers reported in September's online issue of the journal Epidemiology and Infection.

Hands should be washed for a full 20 seconds, but the water doesn't have to be hot, said hand hygiene expert Allison Aiello of the University of Michigan in Ann Arbor. It's a myth that warmer water kills more pathogens — a faucet can't make the water hot enough for that.

"While you're doing the wash, you want to make sure you hit the palms of your hands, in between the digits and under the nails," she demonstrated. "Then you move to the back part of the hand also, and you go somewhat up the wrists, too."

Soap scrubs skin and lifts up microbes so they can be rinsed away. Then the hands should be completely dried because microbes like moisture.

Soap and water works best, experts said, but a hand sanitizer will work in a pinch as long as it contains at least 60 per cent alcohol. The liquid won't remove soil and dirt, but does kill most bacteria and viruses.

Russian roulette with germs

Another recent study estimated that people touch their face about 15 times an hour, or once every four minutes. Each touch is like playing a kind of bacterial Russian roulette, since hands are loaded with germs and every touch could deliver pathogens to sensitive cells in the mouth, nose and eyes.

The eyes are connected to the respiratory tract through the sinuses in the face and mucous membranes of the eyes, said virologist Earl Brown of the University of Ottawa. Viruses can enter the respiratory tract through the sinuses.

At the Ontario Science Centre in Toronto, researcher David Sugarman uses a substance that fluoresces under ultraviolet light to simulate microbes left on hands after a quick handwashing.

Spots on the palm and base of the finger are often missed, Sugarman said.

Since viruses also spread through the air when people cough and sneeze, handwashing won't stop everything. But some studies suggest it could stop the spread of a quarter of colds and flus.