Injuries related to hot-water bottles are at a five-year high in New Zealand and young women are the most at risk of being harmed.
Accident Compensation Corporation figures reveal 900 claims were made in New Zealand last year for hot-water-bottle-related injuries - the most of any year since 2014 - at a cost of nearly $650,000.
Of the 900 claims last year, 70% of the injured were females, the Otago Daily Times reports.
Those making the most claims for injuries related to hot-water bottles last year were aged between 20 and 29 (159 claims) followed by people aged 10-19 (123 claims).
Last year, 91% of such claims were for burns, 5% for laceration and punctures and 2% for soft tissue injuries.
Of the 49 claims made by people in Otago last year, 78% of them were females and the age bracket with the largest representation was between 20 and 29 (31%).
Third-year University of Otago students Olivia Hammond (19) and Karina Robins (20) use hot-water bottles in their flat in Leith St, North Dunedin.
Miss Hammond, of Tuatapere, said she had been raised using hot-water bottles and her family had taught her to take precautions.
"I've never been allowed one without a cover.''
Miss Robins, of Pleasant Point, said she started using them regularly during her first year at university despite her mother - who is a nurse - being against them.
"She's seen so many horror stories. When she first started nursing, a 4-year-old came in with burns everywhere from a hot-water bottle.''
To stay safe, she never filled her bottle with boiling water but she had a "bad habit'' of lying on her bottle.
"I put mine under my stomach and lie on top of it.''
They used hot-water bottles because they were cheaper to use than other heating sources, such as electric blankets, Miss Robins said.
"They are cost-efficient.''
Young women could be more prevalent in the ACC data because they had just left home and were trying to reduce the cost of their power bills.
A male student living in their flat, who slept in its coldest room, never used a hot-water bottle.
She believed men felt the cold less than women so did not use hot-water bottles.
Miss Hammond said she believed men went without because using one could be considered a sign of weakness.
"They're just trying to be tough.''
Burn Support Charitable Trust spokeswoman Michele Henry said the ACC data was "frightening''.
"That's the people who are coming forward. I think the number of people being injured would be higher.''
New hot-water bottles should have safety instructions included but did not.
Dunedin Hospital emergency medicine specialist Sierra Beck said she had been working as a doctor in the hospital's emergency department for more than 18 months.
Before that she worked in an emergency department in Atlanta, in the United States, for six years.
She had never seen anyone harmed by a hot-water bottle and expected injuries to be treated more in primary care.
She speculated more younger women were being injured because they used hot-water bottles when dealing with cramps.
Sleeping with hot-water bottles in the United States was uncommon as houses were warmer there due to the prevalence of central heating.
"My first exposure to hot-water bottles was in the movie Hunt for the Wilderpeople.''
Hot-water bottle safety tips
• Never use boiling water to fill a hot-water bottle as it can cause the bottle to split or leak.
• Use very hot water.
• Don't overfill.
• Firmly close the top before using.
• Cover or wrap the bottle in a towel before using.
• For children and the elderly, use the bottle to warm the bed, then remove it before they get in to bed.
• Regularly check bottles for splits and perishing and replace damaged bottles.
• Don't lie or sit on a bottle.
• Check for a safety standard stamp on the bottle. The accepted versions of the British Standard are BS 1970:2012, BS 1970:2006 or BS 1970:2001.
SOURCE: BURN SUPPORT CHARITABLE TRUST