Scientists have developed a toothpaste containing HRT, to help women remember to take their daily dose.
The mint-flavoured paste has been designed with the added hormones to help women deal with the symptoms of the menopause.
Women normally take HRT as a pill, cream, patch or nasal spray.
Around 2.5m women in Britain use HRT.
Recent research showed women taking hormone replacement therapy are at higher risk of developing breast cancer, stroke or a blood clot in the lung than those who do not.
But they are at less risk of developing colorectal cancer or a hip fracture.
Details of the toothpaste were revealed at the American Society of Reproductive Medicine.
It is infused with estradiol, a synthetic version of the female hormone oestrogen.
This allows the hormones to be absorbed into the lining of the cheek, and then on into the bloodstream.
Researchers from Eastern Virginia Medical School tested the toothpaste on 15 women aged between 40 and 65.
They found that brushing once a day for a week with the paste delivered enough oestrogen to relieve menopausal symptoms such as hot flushes and mood swings.
Hormone levels in the blood remained high enough 24 hours later to relieve symptoms.
However, in three of the patients, blood levels of the hormone were too low to help.
The researcher, Dr David Archer, said men who used the paste by accident were unlikely to be affected, but a daily oestrogen dose could lead to them developing breasts and a loss of libido.
He told a national newspaper: “A woman who kissed a man after she had been using that toothpaste, even if she was giving him a long kiss, wouldn’t be doing him any harm.”
Dr Val Godfree, deputy director of the Amarant Trust, which advises women on HRT use, told BBC News Online: “We have known for some time that you can deliver oestrogen this way.
“Obviously it is in the first stage of development, and it could only be used on its own if women have had a hysterectomy, for those who haven’t need progesterone.”
But she added: “There is quite a wide range of options at the moment, one does wonder why one needs another. But generally, we support more choice.”
Revision date: June 18, 2011
Last revised: by Sebastian Scheller, MD, ScD