The analysis of hair for a broad array of elements and chemicals as a way to diagnose the cause of childhood diseases such as autistic spectrum disorder has no scientific basis. Such assays may not be reliable: hair collection is not precise and it is a heterogeneous matrix; chemicals in hair may not be distributed evenly from the root up the shaft; the assays used may not be accurate technically; and hair can easily be contaminated by external residues of dust, shampoos, conditioners, or other hair treatments. Reports of finding of various metals, etc., can create severe anxiety in the families requiring further testing by other means. Historically, testing by standard means fail to verify the apparent exposure reported by hair analysis.