The acute toxicity of ethanol is very low. Ingestion of ethanol can cause temporary nervous system depression with anesthetic effects such as dizziness, headache, confusion, and loss of consciousness; large doses (250 to 500 mL) can be fatal in humans. High concentrations of ethanol vapor are irritating to the eyes and upper respiratory tract. Liquid ethanol does not significantly irritate the skin but is a moderate eye irritant. Exposure to high concentrations of ethanol by inhalation (over 1000 ppm) can cause central nervous system (CNS) effects, including dizziness, headache, and giddiness followed by depression, drowsiness, and fatigue. Ethanol is regarded as a substance with good warning properties.
Tests in some animals indicate that ethanol may have developmental and reproductive toxicity if ingested. There is no evidence that laboratory exposure to ethanol has carcinogenic effects.
To discourage deliberate ingestion, ethanol for laboratory use is often "denatured" by the addition of other chemicals; the toxicity of possible additives must also be considered when evaluating the risk of laboratory exposure to ethanol.