Those who work with cell cultures are certainly familiar-ized with the ritual of sanitizing everything that goesinto the cabinet or into the incubators with 70% ethanol,as is recommended by all the rules of aseptic techniquesand good cell culture practices. In spite of its eVective-ness in preventing microbiological contamination of thecultures, this gesture may have some undesirableconsequences.Probably, the research groups that study the eVects ofethanol on cell cultures are more conscious about therisks of sanitizing all the material with 70% ethanolbecause they need to guarantee that they have ethanol-free control samples. Thus, these groups routinely quan-tify ethanol in the culture medium to con Wrm the ethanolconcentrations used in their studies. However, the scien-tiWc community must be aware that when 70% ethanol isused on cell culture as a surface sanitization process, ifcautions are not taken, the cells will be exposed to highethanol concentrations. These high concentrations areachieved because, under normal cell culture conditions,the cell culture plates have appropriate venting systems(as they should have, otherwise the cells will not be oxy-genated) and generally, both cabinets and incubatorshave an ethanol-saturated atmosphere due to thefrequent sanitization procedures. Without additionalprecautions, ethanol concentrations of 0.5 mM are easilyattained, and depending on the ethanol-saturation of thecabinets or incubators, these concentrations can reachvalues of 5 mM as illustrated in Fig.1, which representsthe ethanol concentrations detected on 14 independentexperiments where no precautions were taken to avoidthe exposure of the medium to ethanol. Both theseconcentrations have proven eVects on cell function(Charness et al. 1994; Smith and Gong 2007). In fact, itis well described that ethanol, as a microsomal and mito-chondrial enzymatic inducer (CYP2E1, ADH-I), caninXuence the metabolism of several endogenous andexogenous compounds causing eventual antagonisms,synergisms or potentiations that will necessarily aVectthe Wnal results of the experiments (Jang and Harris2007).In addition, by itself, ethanol can directly or indirectlyalter the normal cell function, inXuencing cell survival,redox status, receptor functions, mitochondrial homeosta-sis, cell signaling, among others (Wu et al. 2006), and alsoaVecting the activity of infectious agents such as hepatitic Cvirus (Trujillo-Murillo et al. 2007).Thus, some precautions must be taken to minimize this“contamination” with ethanol: 70% ethanol used to sanitizesurface and objects should be completely dry before theXasks or plates are opened and these should not be sprayedwith 70% ethanol between coming out of the cabinet andgoing into the incubator (but obviously, in between, contactwith other surfaces is forbidden).These concerns are crucial for every lab working withcell culture and must be taken into account during the data