ALDH2 is a gene that provides instructions for making an enzyme called aldehyde dehydrogenase 2. This enzyme plays a crucial role in breaking down acetaldehyde, a toxic byproduct of alcohol metabolism. Proper functioning of ALDH2 helps prevent the accumulation of harmful substances in the body. Individuals with certain genetic variations in the ALDH2 gene may have reduced enzyme activity, leading to a condition known as ALDH2 deficiency. This deficiency can cause unpleasant reactions to alcohol consumption, such as flushing, nausea, and increased heart rate, making it difficult for affected individuals to drink alcohol safely.