Introduction In the last twenty years, hair testing gained considerable interest in forensic toxicology. However, the possibility of a false positive result due to external contamination is still a challenge to analysts. Although there are already several published methods on hair decontamination, some challenges remain, for example, uncertainties concerning sample integrity or absence of migration of the contamination towards the hair interior due to swelling. So far and to our knowledge, the method proposed by Cairns et al. (Cairns, T. et al, Forensic Sci. Int . 145 (2004) 97 – 108) seems to be the only one to fully fulfill the requirements of the Society of Hair Testing. Nevertheless, the disadvantages of this method are the number of human resources needed and the fact that it is time consuming (at least, 3 h 45 min). Herein we present a contactless alternative using supported ionic liquids for the decontamination applied to opiates and cannabinoids. Methods The ionic liquid I, 021–05 was supplied by Solchemar with purity above 98%. The ionic liquid was used to coat a grade 403 cellulosic membrane (30×55 mm) supplied by Ahlstrom. Hair samples with opiate contamination were produced by soaking in 1 μg/mL solution of both morphine and 6-MAM for 1 h. For the cannabinoids contaminated samples, they were flushed with hashish smoke for 7h. For the decontamination experiments, 20 mg of hair were transferred into a glass tube, as well as the supported ionic liquid and they were heated together at 120 °C for opiates and at 100 °C for cannabinoids, both overnight. All the samples were analyzed according to the procedures used in the laboratory, which are validated and published. Results Using previously optimized conditions, the externally contaminated hair samples were decontaminated by our method and by that proposed by Cairns et al. The results were then compared through the analysis of the efficiencies differences. In the case of opiates, the average efficiency difference revealed that our method presented slightly higher efficiency (~4%) that that of Cairns et al. Still, we considered this difference not significant enough to state that the developed method is better. Nevertheless, it allowed us to obtain comparable results. For cannabinoids, the results showed that the present method was able to remove (in average) ~20% more THC than the method of Cairns et al. Although several laboratories only detect and quantify THCCOOH, there are still many that are only able to detect and quantify THC. Furthermore, SEM images revealed the absence of morphological changes in the hair samples after treatment with our method. Conclusions The developed method seems to overcome some problems associated to other methods (e.g. methanol washing): since it is contactless it preserves the sample integrity and does not promote removal of drugs from inside the hair matrix. Although the authors are aware that a decontamination time of 16 h may be considered a disadvantage, it is important to remark that the presented method allows the simultaneous decontamination of many samples (possibly more than 100, depending on the size of the oven) and the process can be carried out overnight without the presence of any technician. The authors are convinced that the present method represents a significant breakthrough towards an easy and efficient procedure for hair decontamination, which is capable of providing great laboratory throughput.