The correct terminology here would be the use of hair in toxicology. Toxicology is a study of the effects of chemicals on the human body. This can be done on people while they are alive or after death as a means to determine the cause of death.
Testing hair during toxicology is a relatively simple and non-invasive method. Also, hair absorbs a lot of chemicals from the body which can provide a comprehensive idea of what the person whose hair is being tested has or had been exposed to. Some of the substances that are revealed by testing hair include heavy metals, alcohol, cocaine, etc.
Toxicology is not a simple thing to explain as it involves using several techniques to determine the chemicals that are contained in the sample being analyzed.
You would need to read a lot of material on this topic that has already been published to gain the information for writing your research paper.