The technology works by reducing blood flow to hair follicles, lowering the uptake of chemotherapeutic toxins.
Women wear the caps for half an hour before the session, while the chemotherapy is absorbed into the body, and for up to two hours afterwards. In one study, doctors at Baylor College of Medicine in Houston, Texas, assessed 182 women with breast cancer undergoing chemotherapy.
Two thirds used the cooling caps while having the treatment and a third did not.
Of the patients who received scalp cooling 51 per cent retained at least half their hair.
A second study at the University of California, San Francisco, assessed 122 patients, with two thirds of those who used the caps keeping their hair. In all instances, the women who did not wear a cooling cap lost all their hair.
Both studies, published in the JAMA medical journal, were funded by companies which make the caps - Paxman Coolers and Dignitana.
Dany Bell, treatment and recovery programme lead at Macmillan Cancer Support, said yesterday: "Losing your hair can be one of the most distressing side effects of chemotherapy and the impact on a person's wellbeing and sense of self can be profound.
"There's more to treating someone with cancer than simply targeting the illness - it's essential that treatment takes a holistic approach to ensure all aspects of a person's wellbeing are managed. This study is promising as it suggests there's a possible solution to hair loss. If you've been diagnosed with cancer, we would advise speaking to your medical team about the options available."
Jane Murphy, clinical nurse specialist at Breast Cancer Care, said: "Women with breast cancer tell us hair loss is far more than just physical and can have an enormous emotional impact - for some it is the most traumatic moment of their diagnosis and treatment.
"So more time dedicated to working out how to reduce these distressing side-effects is essential.
"However, it's important to remember that a cold cap is not right for everyone. It doesn't eliminate hair loss for everybody and can add hours on to an already draining chemotherapy appointment." Some 55,000 women are diagnosed with breast cancer in the UK each year, and 18,000 of them have chemotherapy at some point.
Most patients lose at least some of their hair, a gradual process which starts within two or three weeks of beginning treatment. It usually then grows back after chemotherapy has finished.
