Alcohol allergy, also known as ethanol allergy, occurs because normally, ethanol in the body is converted into acetaldehyde. People with alcohol allergies lack the enzyme needed to convert acetaldehyde, therefore cannot expel acetic acid from the body, resulting in acetaldehyde poisoning and various allergic symptoms. People who can consume large amounts of alcohol usually have a higher amount of this acetaldehyde converting enzyme, allowing them to quickly convert it without experiencing poisoning or allergic symptoms. Alcohol allergies are mostly linked to an allergic constitution; thus, individuals with this constitution will display various allergic symptoms upon exposure to alcohol, the allergen.