Concerns have been raised about germs being spread in offices after a study showed workers use their phones or eat food while on the loo.
A survey of 1,000 employees found that a third make calls or play games on their phone and one in 12 consumes food or drink when they go to the toilet.
Initial Washroom Hygiene said its research revealed that two out of five office workers avoided shaking hands with a colleague who had just left a washroom.
The study, to mark Global Handwashing Day, found that most people do wash their hands after going to the loo.
Dr Peter Barratt, of Initial Washroom Hygiene, said: "As we approach the winter months when Norovirus outbreaks and flu pandemics tend to occur, it's even more important that people remain vigilant with their hand hygiene.
"Employers have an important role to play in supporting their workers' hand hygiene and good health.
"Simple initiatives like notices reminding workers to wash, dry and sanitise their hands after visiting the washroom, before eating and when hot-desking as well as discouraging the use of mobile phones in the washroom, can make a huge difference.
"Creating a clean, pleasant and well-stocked washroom is also an effective way to support workers' hand hygiene and overall health."