Taken from non-dyed new growth hair at the nape of the neck, a hair analysis can reveal minerals excreted by the body from a month or more in the past. When interpreted along with current tests of blood and urine, mineral deficiencies and heavy metal toxicities could be brought to light. However, the test is unreliable where people are poor excretors. Hair analysis, therefore, is not used to diagnose, but is a screening test for heavy metal toxicity and helpful in monitoring detoxification.
