Alcohol intolerance describes a condition where an individual experiences unpleasant reactions almost immediately after consuming alcoholic beverages. This reaction stems from the body’s inability to process alcohol efficiently due to metabolic challenges related to enzyme function. It is distinct from an alcohol allergy, which involves an immune system response to a component in alcohol, potentially triggering severe reactions like hives, swelling, or difficulty breathing.
How the Body Processes Alcohol
The human body metabolizes alcohol, or ethanol, primarily in the liver through a two-step enzymatic process. First, an enzyme called alcohol dehydrogenase (ADH) converts ethanol into acetaldehyde, a highly toxic compound. Acetaldehyde is responsible for many of the unpleasant effects associated with alcohol consumption.
Following this, another enzyme, aldehyde dehydrogenase (ALDH), quickly breaks down acetaldehyde into acetate, a much less harmful substance. Acetate is then further broken down into carbon dioxide and water, which the body can easily eliminate. This efficient conversion process prevents the buildup of acetaldehyde.
Genetic Factors
A primary cause of alcohol intolerance is a genetic variation affecting the aldehyde dehydrogenase 2 (ALDH2) enzyme. This specific genetic change can result in a less functional or even non-functional ALDH2 enzyme. When the ALDH2 enzyme is impaired, the body struggles to convert acetaldehyde into acetate effectively.
The accumulation of acetaldehyde in the bloodstream triggers a range of noticeable symptoms. These can include facial flushing, also known as “alcohol flush reaction,” along with nausea, vomiting, rapid heartbeat, and headaches. This genetic predisposition is notably common among individuals of East Asian descent, where up to 50% of the population may carry the ALDH22 variant.
Immune-Mediated Reactions
Beyond genetic metabolic deficiencies, some individuals experience alcohol intolerance due to sensitivities involving certain compounds in alcoholic beverages. These reactions are not true allergies, as they do not involve the immune system’s typical allergic response, but rather sensitivities to specific substances. Histamine intolerance is one such sensitivity, where the body has difficulty breaking down histamine, a chemical naturally present in fermented drinks like red wine and some beers.
Individuals with histamine intolerance may lack sufficient diamine oxidase (DAO), an enzyme that helps break down histamine in the gut, or alcohol itself can inhibit DAO activity. This leads to symptoms such as flushing, headaches, nasal congestion, and gastrointestinal discomfort. Another factor is sulfite sensitivity, as sulfites are commonly used as preservatives in alcoholic beverages, particularly wine and beer. People sensitive to sulfites might experience asthma symptoms like wheezing, hives, or abdominal pain.
Medications and Other Health Conditions
Certain medications can interfere with alcohol metabolism, leading to intolerance-like symptoms. Disulfiram, a medication prescribed to deter alcohol consumption, specifically inhibits the ALDH enzyme, causing acetaldehyde to build up and produce immediate, unpleasant reactions. Other medications, such as some antibiotics like metronidazole, certain antifungals, and some diabetes medications, can also induce a disulfiram-like reaction when combined with alcohol.
Some underlying health conditions can also manifest with alcohol intolerance. Hodgkin’s lymphoma, a type of cancer affecting the lymphatic system, is rarely associated with alcohol-induced pain. Patients with Hodgkin’s lymphoma may experience pain in affected lymph nodes shortly after drinking alcohol.