The problem of vaginal dryness among women undergoing breast cancer treatment is widely under-recognised and often unmentioned by the women themselves. "Between 50 to 80 per cent of women who are being treated for oestrogen-receptor positive breast cancer suffer the side effect of vaginal dryness," says Maggie Walsh, a nurse who has worked with breast cancer patients for 20 years and is a breast cancer survivor herself.

Despite the frequency of this side effect it is little mentioned. "It is estimated that around 70 per cent of women who are breast cancer survivors will not voluntarily raise this issue with healthcare professionals, and many of these professionals do not broach the issue either, most likely because of embarrassment and lack of training to help deal with the issue," she says.

The problem is set to become more widespread as breast cancer survival rates increase. There are already 500,000 breast cancer survivors in the UK and by 2040 it is forecast that there will be 1.7 million.

And it is an important issue for many individual women, their partners and families. Vaginal dryness commonly leads to painful intercourse which means the affected woman's libido can dwindle, sometimes leading to problems with her partner. The strains on the relationship may ultimately result in relationship breakdown, divorce and family break-up.

Unfortunately there is little that can be done at present to prevent vaginal dryness as a side effect of hormone therapy for breast cancer, because of the way the anti-oestrogen drugs used in breast cancer treatment work. Tamoxifen, the most widely prescribed drug for breast cancer in pre-menopausal women, has vaginal dryness as one of its side effects. Walsh says: "Some eight per cent of women taking tamoxifen complain to medical professionals about vaginal dryness as a side effect, but it is likely that there is a much larger unreported problem."

Post-menopausal women with breast cancer face a double problem: vaginal dryness is one of effects of the menopause in many women, caused by falling levels of oestrogen, which helps keep the vagina naturally lubricated and flexible and helps prevent thinning of the vaginal walls. However, the aromatase inhibitors that are widely used to treat breast cancer in post-menopausal women are designed to suppress oestrogen. They work by blocking the enzyme aromatase, which turns the hormone androgen into small amounts of oestrogen in the body. This means that less oestrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells, so the drugs have a protective effect against breast cancer.

However the reduced levels of oestrogen mean the chances of vaginal dryness and vaginal atrophy are increased. "The drugs exacerbate the existing natural tendency to vaginal dryness in post-menopausal women, making it a major problem for those receiving hormone therapy for breast cancer," says Walsh.

It is not a short-lived side effect - many women are treated with these oestrogen-blocking drugs for up to ten years after their initial cancer treatment.

So what can be done to improve the problem? For many healthy post-menopausal women the vaginal dryness problem can be eased by hormone replacement therapy (HRT). However, this involves supplementation with the hormone oestrogen, and it is not recommended for women whose breast cancer has been oestrogen-driven, as many breast cancers are.

"There is some evidence that vaginally-applied oestrogen preparations, which can help alleviate vaginal dryness and atrophy, are safe for breast cancer survivors who are taking tamoxifen but often women who have had oestrogen-driven breast cancers are naturally reluctant to use them," says Walsh. These vaginally-applied oestrogen preparations are not recommended for women taking aromatase inhibitors.

Many women turn to vaginal lubricants instead as a safer option. Personal lubricants can minimize the friction involved in intercourse and reduce the risk of tearing of the vaginal walls, thus reducing pain and the chances of infection.

Most are water-based, which while reassuringly natural, means they can be quickly absorbed into the vaginal wall, so the lubricant can soon turn from smooth to sticky, thus reducing its lubricant effect.

A few are based on silicone, which builds a protective film on the skin without blocking the pores or impairing the breathability of the skin and the mucous membrane. In addition, silicone particles are larger than the pores of human skin, so they cannot be absorbed by mucous membranes such as the vaginal walls, so silicone-based lubricants retain their lubricant effect for longer. Like water-based lubricants they can be used with condoms.

Vaginal moisturisers may also help, and lifestyle changes may help counteract vaginal dryness in some women. "Smoking reduces blood flow overall and can exacerbate a tendency to dryness in the tissues, so giving up smoking may help," says Walsh.

Sexual intercourse increases the blood flow to the vaginal area which increases the flow of natural lubrication but if intercourse is painful because of vaginal dryness, it may be hard for women to countenance an increase.

Meanwhile avoiding the use of perfumed soaps and similar products in the vaginal area may help, Walsh advises.

Perhaps bringing the problem of vaginal dryness to greater attention within the medical profession will help stimulate more research into treatments.

"NICE guidelines on the diagnosis and treatment of the menopause are anticipated for announcement in October 2015, so GPs and medical professionals should hopefully be more proactive in dealing with it - and perhaps the problem of vaginal dryness will get more attention," says Walsh.