Alcohol abuse is a significant medical and social problem. At sufficiently high doses, ethanol, the active ingredient of alcoholic beverages, and others can cause both short-term (such as inebriation) and long-term (such as cirrhosis of the liver) toxic effects in humans. Thus, concern has been raised about the possible health consequences of using ethanol for alcoholic hand rubs. Since the intrinsic toxic effects of ethanol require its entry into the bloodstream, we evaluated ethanol blood concentrations using 3 different ethanol-based hand rubs.
The median baseline values of ethanol (< 0.07 mg/L) and acetaldehyde (0.20 mg/L) indicated ethanol abstinence of volunteers before the initiation of the experiments, since all median observed baseline values were below the maximum physiological level of 0.32 mg/L for ethanol and 0.31 mg/L for acetaldehyde . However, individual baseline ethanol concentrations ranged from non-detectable concentrations to a maximum of 1.70 mg/L. This is not unexpected since ethanol is produced through fermentation by fungi and other intestinal microorganisms, and is found at low levels in the blood and exhalation of individuals otherwise abstinent . The individual blood levels determined in our study at baseline vary to some extent due to individual factors influencing the production, absorption and metabolism of ethanol such as activity of alcohol dehydrogenase, alimentation and gender [36, 37].
We were able to demonstrate that following excessive hygienic or surgical hand disinfection only 0.5% to 2.3% of the applied ethanol is absorbed. This excessive exposure, however, will rarely occur in clinical practice. Albeit that, we were compelled to chose this particular experimental design since the literature does not offer data on exact absorption rates after hand disinfection.
Our findings are important to have confidence in the safe use of ethanol-based hand rubs. Blood ethanol levels that result in diminished fine motor coordination range around 200 – 500 mg/L and impaired judgement around 500–1000 mg/L . If a surgeon carries out three surgical hand disinfection with hand rub A (containing the highest concentration of ethanol) over 6 hours (one hand disinfection every two hours) using e.g. a total of 20 mL hand rub, he will be exposed to 15.1 g ethanol every two hours. According to our results, approximately 0.7% of the applied ethanol will be absorbed, equivalent to 106 mg ethanol. Assuming 70 kg body weight and 40.6 L total body water for an average man, or 60 kg body weight and 28.8 L total body water for an average woman, the systemic availability of ethanol after this surgical hand disinfection will be 2.61 mg/L in a man, or 3.68 mg/L in a woman, respectively. These findings are in line with results reported in a recent study by Miller et al.  where five subjects applied repeatedly (50 times over 4 hours) 5 mL of an ethanol based hand rub (62% denatured ethyl alcohol) to both hands and rubbed until dry. The authors reported that blood ethanol level upon completion of the applications of the ethanol/based hand rub was less than 5 mg/dL in all 5 study participants.
In comparison, it should be pointed out that a single alcoholic drink contains about 12 g of ethanol , corresponds to a dose of 170 mg/kg for a 70 kg adult, and produces a peak blood ethanol concentration of 250 mg/L. Fruit juices may contain up to 3 g ethanol per L , and an apple juice may well contain 1 g ethanol per 500 mL. Assuming a resorption rate of 90%, drinking half a litre of apple juice will result in a concentration of 0.17‰ ethanol in a 75 kg man or 0.25‰ ethanol in a 60 kg woman .
A hand rub must be safe and effective. Pertaining to safety, we are confident to conclude that under clinical conditions the use of ethanol-based hand rubs does not lead to intoxicating levels of alcohol in the peripheral blood. The efficacy of alcohol-based hand rubs, however, depends on the concentration of alcohol. For patients safety it is therefore a first and foremost prerogative to ensure the efficacy of a hand rub. In light of our results clearly showing that ethanol absorption corresponds to exposure dose and time, it is tempting to speculate that the theoretical risk of systemic toxicity for health care workers could be further minimized by shortening the application time of ethanol in surgical hand disinfection to a minimum time necessary for the alcohol to achieve the required efficacy. This might help to reduce the very small risk of systemic toxicity for the healthcare worker even further. Especially for surgical hand disinfection recent data indicates the possibility of reducing the current recommendation of 3 minutes application time since it was shown that an application time of 1.5 minutes was equally as effective as 2 or 3 minutes . However, so far this has only been shown with a propanol-based hand rub [43, 44]. Furthermore, it has been reported that in consecutive surgical procedures of less than 60 minutes duration a 1 minute application may be sufficient to ensure adequate efficacy .
Our study has several limitations. We did not take into consideration that the average rate of metabolism for ethanol is 150 mg/L within 1 h or 0.15‰/h, equivalent to 12.5 mg/L within 5 minutes . However, based on this rate of metabolism and an application with longer intervals, the true ethanol blood concentrations will be lower than those calculated in our experimental model. Yet, our setting does not allow predictions about the potential ethanol kinetics for a cumulative absorption over multiple days or weeks of use. Also, our test model did not distinguish between dermal and pulmonary absorption. Prediction of blood ethanol concentration following exposure to ethanol vapours must consider the concentration of ethanol in air, the duration of exposure, breathing rate, absorption of ethanol across the lungs, and the physiological elimination rate of ethanol. The absorption of ethanol across the lungs and the physiological elimination of ethanol are the only two factors more or less constant. In humans, it has been demonstrated that 55% to 60% of inhaled vapours are absorbed into the bloodstream . The clearance rate of ethanol from the blood is about 150 mg/L/hr  but may be as high as 230 mg/L/hr . These rates correspond to elimination of 83 mg/kg/hr to 127 mg/kg/hr, or about 6 to 9 g of ethanol per hour for an average adult. However, these considerations are only of academic, but not of practical relevance, since healthcare workers rarely use ventilation masks when applying alcohol-based hand rubs. As in practice healthcare workers also will be exposure to alcohol vapours, we considered the experimental design of this study to be closer to clinical reality. Indeed, some of the observed absorption is certainly due to pulmonary uptake. If for example 200 mL of hand rub A is applied within 80 minutes, a total of 150.1 g ethanol will evaporate into the air. If no air exchange takes place, this will result in an ethanol saturation of 4.1 g/m3 air, which is approximately two times above the maximum occupational exposure concentration of 1.9 g/m3. Since both windows and the door of the test room were open, air exchange took place. Nevertheless, it can not be ruled out that some of the ethanol in blood was taken up by respiration.
Although this study provided answers to some hitherto unsolved questions, it can not answer if the use of ethanol-based hand rubs is acceptable for those individuals in which religion or culture prohibits alcohol, i.e. Muslims. Indeed, the data clearly show that after hand disinfection using ethanol-based hand rubs absorption – although non-intoxicating and safe for human level – does occur. This has at least two implications. For Muslims, any substance or process leading to a disconnection from a state of awareness or consciousness is 'haram'. We were able to show that consciousness definitively can not be altered by using different ethanol-based hand rubs. However, this still does not mean that their use is 'halal'. Some Muslims believe that if something taken in a large quantity acts as an intoxicant, then it is 'haram' to even take in a small quantity of that. Yet, others do not share this view. Alcohols can either be 'khamr' or 'non-khamr'. 'Khamr' alcohols can be said to be alcohol derived from dates and grapes while 'non-khamr' alcohols are not derived from any of these two. The ruling regarding 'khamr' is that even the most minuscule amount of it is 'haram', regardless of whether it intoxicates or not, while the ruling considering other alcohols is that only that amount is 'haram' which intoxicates. A small amount which does not cause intoxication is not 'haram'. The only condition is that it must not be drunk for amusement and pastime. If it is used to gain strength, to digest the food, or for medical reasons then it is permissible as long as it does not intoxicate. However, since ethanol is classified as 'khamr', its use could be regarded 'haram', regardless if it could intoxicate or not.
Because this matter could potentially impede the worldwide use of ethanol-based hand rubs, particularly in predominantly Islamic regions, it demands attention and clarification. Yet, at many Saudi Arabian hospitals, use of alcohol-based hand rub has been permitted since 2003, and no difficulties or reluctance to adopt these formulations have been encountered . Moreover, there is an encouraging acceptance in Muslim countries indicating that the use of alcohol-based hands is acceptable to most Muslim health-care workers.