The assessment of alcohol consumption behavior in hair is well established in forensic toxicology. The Society of Hair Testing (SoHT) recommends the direct alcohol markers ethyl glucuronide (EtG) and fatty acid ethyl esters (FAEE) for the detection of past alcohol consumption. In this study, we investigated if detox shampoos which are sold online can have an impact on EtG or FAEE concentrations in hair. According to customer reviews, positive drug testing results could be avoided after long‐term incubation with shampoo under a swimming cap. To evaluate the potential of four detox shampoos, we incubated distal hair samples from three subjects, obtained during a standard haircut, for 2.5, 5, 7.5, and 10 hours. For EtG, three shampoos performed similar to deionized water. The fourth shampoo showed additional heavy washout effects with a decrease of up to 86% after 2.5 hours. For the apolar FAEE, no washout was observed. Incubation with two shampoos resulted in increases in FAEE concentrations due to FAEE being present as shampoo ingredients. Further investigation of EtG washout in proximal forensic hair samples (n = 9) with the most potent shampoo showed a mean decrease in deionized water of 23% ± 25%, and a decrease by the use of detox shampoo of 73% ± 12%, compared to non‐incubated hair after 8 hours. In conclusion, detox shampoos proved to have the potential to alter EtG and FAEE concentrations in hair during in vitro experiments.