Lysergic acid diethylamide (LSD) is a powerful hallucinogen, active at very low dosages, with, as a direct consequence, potential difficulties to be detected and quantified in a clinical or forensic context, in body fluids and even more in hair. The aim of this work is to review literature data related to hair analysis of LSD with a particular focus on the main issues encountered in LSD detection in hair. Results of LSD investigation in hair remain difficult to interpret regarding the very sparse data available on LSD concentrations in hair (n=10). The possibility of pubic hair contamination by urine, as well as the lack of data about LSD incorporation and stability in pubic and head hair, further challenges the interpretation of negative or positive results. The absence of LSD in head hair should be carefully considered, as it does not formally exclude LSD consumption. In all cases of positive results, the interpretation of LSD concentrations in hair remains uncertain and it seems utopian to distinguish repeated intake from single exposure using LSD hair concentration values. Furthermore, a positive result in pubic hair cannot be used to formally prove repeated use of LSD, even in the case of a documented recent use of LSD.