Researchers prefer the term immunotherapy because it would treat, not prevent, cancer.

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"We're already using the fact that 5t4 is found in cancer cells, but not in normal tissue, to design immunotherapy against it and are testing two such systems in clinical trials, " said Professor Stern.

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Another potential benefit of immunotherapy is that if it's given early enough, it may prevent children with an allergy or two from developing many more, according to Dr. Canfield.

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Although nearly everyone should consider immunotherapy, Dr. Canfield says, it's not for everyone.

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It is unclear when parts of Asia and Asia Minor began using immunotherapy to prevent smallpox deaths, but in the early 18th century, Lady Mary Worthley Montagu, an English aristocrat stationed in Istanbul, made note of the practice and brought it back to England.

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But there are many unknowns about this treatment, and it's not clear how permanent the state of desensitization is, she said, and this immunotherapy method is not a cure.

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Participants in immunotherapy studies have reported that they learned not to take their regulated allergen doses before exercising because it causes a faster absorption of proteins and can trigger a reaction, she said.

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