People who are bald, have significant baldness or shave their hair do not have enough material to collect a sufficient amount of hair to perform an analysis.
However, it is possible to use other hairs to perform a hair analysis. For example, pubic hair, axillary hair (under the armpits), hair on the chest, arms or legs can be analysed.
Similar to hair, the presence of a substance in a hair indicates with certainty exposure to that substance. However, where comparative data are available for hair, it is not possible to extrapolate to other hairs. This is because other hairs may have a different structure from hair and, above all, a different growth rate.