What influence do hair treatments have on the results of a hair analysis?

The application of cosmetic products on the hair (shampoo, detangling cream, colouring) does not modify the hair structure. These cosmetic products do not interfere with the substances sought because the analysis techniques used are selective and specific. 

However, some cosmetic products, such as anti-dandruff shampoos, include substances that can be found in the hair, such as selenium or zinc. 

Hair treatments such as bleaching or perms involving the destructuring of the hair can produce an opening of the scales (epidermis) protecting the internal structure of the hair. This alteration can lead to the incorporation of substances present on the outside of the hair by migration to the inside of the hair. On the other hand, it can also favour the extraction of substances present inside the hair and lead to a loss of information. 

Certain hair treatments can therefore have an impact on the results of a hair analysis.