Twelve-year-old Kathleen MacIsaac learned that the hard way when she started getting headaches so painful they landed her in the emergency room.

After scans and specialists ruled out a brain tumor or injury, and five different medications failed to make a difference, she began to experiment with alternative treatments. Now, the Woburn sixth-grader has become a big fan of acupuncture, which she says doesn’t hurt at all and is really relaxing.

There’s plenty of evidence to show that acupuncture is an effective treatment for headaches in children, but most doctors wouldn’t have suggested it, and her mother, Lisa, a nurse, admits it felt weird at first to try an approach she hadn’t learned about in school.

Her doctor’s urging, Lisa MacIsaac said, made her more open-minded to such an alternative treatment.

On the other hand, as many as 70 percent of families with chronically ill kids use alternative therapies, according to a new study — and many of them don’t talk about these treatments with their doctors.

Doctors specializing in integrative medicine — the melding of conventional and alternative treatments — say that it’s crucial for patients and doctors to work together to find the safest therapies that are most likely to help children. Doctors need to be more accepting of approaches parents are trying with their kids, they say, and families need to be more willing to discuss these approaches with doctors.

“I’m open to whatever they want to try, as long as I have the opportunity to explore whether it’s going to be helpful or harmful,” said Dr. W. James King, a consulting pediatrician at Children’s Hospital of Eastern Ontario and a leader of the new study, published this month in the journal Pediatrics. “If we can’t show it’s going to be helpful, we want to be sure it’s not going to be harmful.”

It’s not clear whether the use of complementary and alternative medicines — often referred to as CAM — is rising in children, because studies like King’s are just beginning to quantify its use. The definition of CAM varies widely, and can include a wide range of supplements and therapies, from vitamins and herbs, to yoga, acupuncture, massage, chiropractic or osteopathic manipulation, and a Japanese stress-reduction technique called Reiki.

King’s study looked at children in five clinics at two Canadian hospitals: cardiology, gastroenterology, oncology, neurology, and respiratory. The sicker the child, the more likely the family was to use complementary therapies, King said. Children were also more likely to receive alternative treatments if their parents had already tried them. And the older the child, the more frequently parents used alternative therapies, King said, perhaps out of frustration that conventional treatments weren’t working.

That frustration has driven up the popularity of complementary medicine.

“The current widespread interest in this among the general public I think is fueled by dissatisfaction with conventional care that is sometimes perceived as being limited, compartmentalized, specialized, and doesn’t look at the whole person,” said Helene Langevin, director of the Osher Center for Integrative Medicine at Harvard Medical School and Brigham and Women’s Hospital.

Other families, particularly recent immigrants, arrive at the doctor’s office with as much or more faith in remedies indigenous to their home countries as western medicine.

Dr. Sean Palfrey, a professor of pediatrics and public health at Boston University and Boston Medical Center, said he once had a patient, an infant, who was dying of a genetic disease. There was nothing western medicine could do to change that outcome.

The family, originally from Somalia, wanted to “coin” the child, a practice in which a heated coin is placed on the skin to remove harmful substances, leaving red marks and sometimes minor burns. Palfrey said his first instinct was to protect the baby from these burns. But then he realized that the family would feel more at peace if they believed they had tried this remedy first. He discussed ways they could make the ceremony safer for the child and then allowed them to go ahead with it.

Palfrey said he became convinced of the effectiveness of such traditional medicine while working in China, where he saw “hundreds if not thousands of natural substances that are effective in ways that we have not studied in terms of western medicine.”