Why does acetaldehyde accumulation cause acute symptoms such as flushing and nausea when ALDH is deficient, even though BAC may remain unchanged?

• A. ALDH deficiency increases hepatic blood flow which both raises BAC and produces flushing by thermoregulatory disruption, so the symptoms are due to higher BAC values.
• B. Because acetaldehyde directly increases the solubility of ethanol in blood which artificially lowers measured BAC while increasing peripheral toxicity and causing flushing.
• C. Acetaldehyde is a toxic intermediate produced in the liver that causes vasodilation and irritative symptoms; ALDH deficiency slows its clearance so it accumulates and produces these effects independent of unchanged ethanol blood percentages.
• D. When ALDH is deficient, ethanol is rapidly converted to acetate which triggers histamine release from mast cells producing flushing and nausea even though acetaldehyde levels are low.

Answer: (C)