Alcohol intolerance is the medical term for an immediate and unpleasant reaction to consuming alcohol. Common symptoms include skin flushing, nasal congestion, and headaches.

Alcohol intolerance is an immediate unpleasant reaction to consuming alcohol. It typically occurs because of a genetic difference that makes the body unable to break down alcohol efficiently.

This article explains what alcohol intolerance is, including its causes and symptoms. It also discusses how alcohol intolerance differs from alcohol allergy and considers the treatments for each.

What causes alcohol intolerance? 

Alcohol contains metabolites, which are substances produced during metabolism. The primary metabolite of alcohol is acetaldehyde.

Individuals with alcohol intolerance can have a genetic predisposition that prevents a group of enzymes called aldehyde dehydrogenases (ALDHs) from metabolizing acetaldehyde to a nontoxic substance called acetate.

The genetic predisposition for alcohol intolerance is more common among Asian people.

Some health conditions can also cause alcohol intolerance, while others can cause increased alcohol sensitivity. Some people use these two terms interchangeably.

Examples of conditions that can cause alcohol intolerance or sensitivity are outlined below.

Histamine intolerance

A histamine is a chemical that the body releases in response to allergy, inflammation, or injury. If you have histamine intolerance, you lack a digestive enzyme called diamine oxidase, which helps your body break down excess histamine.

Alcohol and other fermented products also contain histamine. Red wine contains particularly high levels.

If you have histamine intolerance, you may experience worse symptoms after consuming alcohol with a high histamine content.

Sulfite sensitivity

Sulfites are preservatives used in the production of certain foods and beverages, including beer, wine, and cider.

Sulfites interact with stomach acid to release an irritant gas called sulfur dioxide, which can cause airway irritation in susceptible individuals. The name for this reaction is sulfite sensitivity.

Sulfite sensitivity is not the same as sulfite allergy. The latter is much more severe and comparatively rare.

Chronic fatigue syndrome

Chronic fatigue syndrome (CFS) is a chronic condition involving pain, insomnia, and severe fatigue that does not improve with rest. A 2023 study found that individuals with CFS are more likely to experience alcohol intolerance.

Study authors speculate two potential causes of alcohol intolerance in people with CFS:

Alcohol may worsen underlying problems with the autonomic nervous system, which regulates involuntary bodily functions like heart rate, blood pressure, and body temperature. High levels of the alcohol byproduct acetate may worsen dysfunction in brain areas with high levels of metabolic activity.Post-viral fatigue

Post-viral fatigue (PVF) is fatigue that first starts during a viral infection but persists after the virus has gone. Scientists are not sure what causes PVF, though immune cells called cytokines likely play a role.

Cytokine numbers naturally increase during an active infection. In PVF, their numbers may remain elevated once the infection has cleared.

Long COVID is a type of PVF that involves new or worsening COVID-19 symptoms months or years after the initial infection.

In a 2023 case study series, four individuals with long COVID reported new onset alcohol sensitivities after having COVID-19. Researchers suggest the causes may be the same as those for CFS, adding that other causes may include neuroinflammation and changes to the gut microbiome.

Can alcohol intolerance develop suddenly?

The sudden development of alcohol intolerance is a common early symptom of CFS. Scientists have not yet identified the reason for this association.

However, the ME Association in the United Kingdom notes that alcohol acts on the central nervous system (CNS), and that people with CFS appear to have a generalized hypersensitivity to drugs that act on the CNS.

What are the symptoms of alcohol intolerance?

Alcohol intolerance can cause an immediate or delayed reaction, with delayed reactions sometimes occurring 20 to 30 minutes after alcohol consumption, according to the ME Association.

Signs and symptoms of alcohol intolerance may include:

skin flushingnasal congestionheadachesnauseavomitinglow blood pressure

Alcohol intolerance vs. allergy

Alcohol intolerance and alcohol allergy may share certain symptoms, but they are two different conditions.

Alcohol intolerance happens when the body cannot properly break down alcohol. Alcohol allergy happens when the immune system mistakenly identifies alcohol as a threat and launches an attack that can affect the entire body.

People can be allergic to proteins in substances used to make alcohol, such as:

grapesyeasthopsbarleywheat

It’s also possible to be allergic to proteins in filling agents, such as egg or shellfish, which manufacturers sometimes use to remove fine particles from alcoholic beverages.

Very rarely, a person may have a “true” alcohol allergy, meaning they are allergic to the ethanol in alcohol. In people with true alcohol allergy, as little as 1 milliliter (mL) of pure alcohol can trigger an allergic reaction. This amount of alcohol is the equivalent of a mouthful of beer.

A true alcohol allergy may cause the following symptoms:

skin rash or itchinessswellingsevere abdominal cramps

In some cases, a severe and potentially life threatening allergic reaction called anaphylaxis may occur. Symptoms may include:

difficulty breathingtightness in the throatnausea and vomitingdiarrheadizziness and faintinga racing hearta feeling of impending doom

If you experience any of these symptoms after consuming alcohol, seek immediate medical care. Without urgent treatment, anaphylaxis can lead to death.

Is alcohol intolerance treatable?

The only way to treat alcohol intolerance is to avoid alcohol.

At the very least, you should limit alcohol as much as possible, especially if it’s making you unwell.

Some people may find relief with diamine oxidase (DAO) supplements, which may assist your body in breaking down histamines. However, research is still limited on DAO supplements. It’s best to discuss with a doctor before trying them.

Is alcohol allergy treatable?

If you have alcohol allergy, the only way to avoid symptoms is to avoid alcohol completely.

If you’re allergic to a specific ingredient in certain alcoholic drinks, switching to a different alcoholic drink may be an option. However, it’s important to read ingredient labels very carefully.

Medications called antihistamines can help treat symptoms of a mild allergic reaction. The medication epinephrine, commonly called an EpiPen, can help treat a severe allergic reaction.

At the first signs and symptoms of a severe allergic reaction, it’s essential to use epinephrine and go to the nearest emergency department for immediate follow-up care.

Takeaway

Alcohol intolerance is an immediate and unpleasant reaction to consuming alcohol. It typically occurs because the body lacks the ability to properly break down alcohol or one of its constituents.

“Alcohol sensitivity” is a term that some people use synonymously with alcohol intolerance. It can occur because of an underlying medical condition.

Alcohol intolerance is not the same as alcohol allergy. An alcohol allergy involves an immune system overreaction to alcohol, which can cause widespread and sometimes life threatening symptoms. Anyone who experiences severe allergy symptoms after consuming alcohol needs to seek emergency care.

Common symptoms of alcohol intolerance include skin flushing, nasal congestion, and headaches. The only way to treat alcohol intolerance is to avoid alcohol or, at the very least, limit alcohol consumption.