"There is sufficient evidence for the carcinogenicity of alcoholic beverages in humans.... Comes this video by Dr. Greger explaining how even small amounts of alcohol, sips, sips that aren't even swallowed, can raise cancer risk:
The occurrence of malignant tumours of the oral cavity, pharynx, larynx, oesophagus and liver is causally related to the consumption of alcoholic beverages.
Alcoholic beverages are carcinogenic to humans (Group 1)."
- IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 44, Alcohol Drinking, Summary of Data Reported and Evaluation, World Health Organization, International Agency For Research On Cancer, January 1998
Studies he cited:
Light Alcohol Drinking And Cancer: A Meta-Analysis, Annals of Oncology, August 2012
Conclusion: Light drinking (defined as up to 1 drink/day) increases the risk of cancer of oral cavity and pharynx, esophagus and female breast.Epidemiology and Pathophysiology of Alcohol and Breast Cancer: Update 2012, Alcohol and Alcoholism, March 2012
"Since there is no threshold level of ethanol for breast cancer risk, the breast is one of the most sensitive organs for the carcinogenic action of alcohol. Healthy women should not exceed one drink/day (equivalent to 10–12 g of ethanol). Women at an elevated risk for breast cancer such as those with a positive family history, benign mastopathy or other conditions associated with an increased breast cancer risk should avoid alcohol or consume alcohol only occasionally."A Single Sip Of A Strong Alcoholic Beverage Causes Exposure To Carcinogenic Concentrations Of Acetaldehyde In The Oral Cavity, Food and Chemical Toxicology, 2011
"Carcinogenic concentrations of acetaldehyde are produced from ethanol in the oral cavity instantly after a small sip of strong alcoholic beverage (that was not swallowed), and the exposure continues for at least 10 min."Salivary Acetaldehyde Increase Due To Alcohol-containing Mouthwash Use: A Risk Factor For Oral Cancer, International Journal of Cancer 2009
"All in all, we conclude that there is a rather low margin of safety in the use of alcohol-containing mouthwash. Typical use will reach the concentration range of 50–150 μM above which adverse effects are to be expected. Till the establishment of a more solid scientific basis for a threshold level of acetaldehyde in saliva, prudent public health policy would recommend generally refraining from using alcohol in such products."