Some people discover their intolerance suddenly, one evening, they drink the same wine as always, and the next morning, their face is flushed with facial flushing, their heart is beating rapidly with a rapid heartbeat, and they have a terrible headache.

Alcohol intolerance can actually be quite common, although it often manifests itself in later years and is not necessarily associated with the first attack of drunkenness. Alcohol intolerance is explained primarily by a deficiency of the enzyme aldehyde dehydrogenase 2. In addition, other symptoms are also possible, from a harmless red flush to a potentially dangerous allergic reaction. A few important points to note:

• Alcohol intolerance is different from an allergic reaction, which requires avoiding alcoholic drinks entirely.
• The development of intolerance may be associated with advancing years, liver disease, or the use of certain medications.
• A wise approach to drinking will be to limit or completely abandon alcohol if you have intolerance.

Let’s take a closer look at the causes of alcohol intolerance, the symptoms that may indicate it, and what to do if intolerance occurs.

Why Do People Develop Alcohol Intolerance?

Alcohol intolerance is associated with the fact that enzymes involved in alcohol metabolism break down alcohol too slowly, leading to the accumulation of toxic by-products. First, alcohol dehydrogenase (ADH) breaks down alcohol into acetaldehyde, which is then broken down by aldehyde dehydrogenase (ALDH2).[1] If this enzyme is deficient, acetaldehyde accumulates in the body, causing the characteristic symptoms of alcohol intolerance.

There are many reasons for this deficiency, but the most common is the genetic one. Approximately 30% of people of East Asian descent, for example, have ALDH2 deficiency, which is why they may have difficulty tolerating alcohol.[2]

This reaction is often referred to as Asian glow. However, there are other reasons why alcohol intolerance may develop. This includes a sensitivity to certain ingredients in the drink, such as:

• Sulfites and other preservatives.
• Histamine, found mainly in red wine.
• Yeast, used in the preparation of alcoholic fermentation.
• Various additives and flavoring agents.

In this case, it is important to differentiate between intolerance to individual components and a more serious allergic reaction, which can be life-threatening. Alcohol can also trigger allergies to other components, for example, wheat or barley, which are used to make many types of beer.

Finally, the development of intolerance can be provoked by diseases or the taking of certain drugs. Thus, cirrhosis of the liver, Hodgkin’s lymphoma, and even the drug disulfiram, prescribed for alcoholism, can be the reason for this inconvenience.

Can Alcohol Intolerance Develop Suddenly?

This is entirely possible, which explains why many people are faced with the fact that they no longer tolerate alcohol as much as before. However, keep in mind that most often, such problems are due to a decrease in the activity of enzymes inherent in every person.[3] One of the reasons for this decrease may be a genetic predisposition, which explains the intolerance to alcohol, often manifested among Asians.

However, even if you do not have a deficiency of enzymes at the genetic level, there is no reason to panic at the sight of the “alcohol glow.” This sometimes happens because hormonal changes, including the level of estrogen, vary during the menstrual cycle, which affects enzyme activity. In addition, the change in estrogen levels associated with menopause can lead to similar effects.

What’s more, a change in weight or constitution can also be the reason. If you have previously been able to drink heavily without feeling any unpleasant consequences in the morning, this does not mean that you have become accustomed to alcohol. Your body may simply have changed, and now you have developed alcohol intolerance.

Finally, alcohol intolerance can be a harbinger of disease, so it is important to consult a physician if you suspect that you have it. In particular, liver function tests should be done, since alcohol intolerance is sometimes the first sign of cirrhosis. Fortunately, this is a relatively rare occurrence, but nonetheless, it is important to recognize the potential dangers.

What Symptoms Can Alcohol Intolerance Cause?

Alcohol intolerance symptoms typically appear during or right after drinking. The next morning, you may experience some of the following effects:

• Flushing skin and/or visible blood vessels, sometimes with hives.
• Increased heart rate.
• Nausea, vomiting, stomach upset, or abdominal cramps and stomach cramps.
• Headache or migraines.
• Congestion, stuffy nose, nasal congestion, or runny nose.
• Low blood pressure.
• Diarrhea.

Headaches, nausea, and dizziness the morning after drinking are uncomfortable symptoms, but they are not the only ones. When intolerance is present, you may also experience typical hay fever symptoms, namely increased swelling of the nasal mucosa, stuffiness, and runny nose. You may also feel that your heart is racing and that your blood pressure has dropped.

Of course, these effects are much more powerful than the unpleasant effects of a normal hangover. This is because, with alcohol intolerance, acetaldehyde accumulates in the body, which takes longer to get rid of.[4] It is useful to track all the effects that occur the day after drinking to determine exactly which of the symptoms is associated with intolerance.

What Is the Difference Between Alcohol Intolerance and Allergy?

It is important to distinguish between intolerance and allergy, which is why you need to understand the key differences between the two conditions.

The main distinction between alcohol intolerance and allergy lies in the involvement of the immune system. Thus, while alcohol intolerance is due to a shortage of enzymes, an allergic reaction is the result of an immune system response and is often much more dangerous.[5]

Symptoms of an allergic reaction include rash and hives, itching, swelling, wheezing, and difficulty breathing. In addition, an allergy can be accompanied by asthmatic attacks, which are potentially life-threatening.

Therefore, if you have ever had an allergic reaction after drinking alcohol that was severe and involved a number of the above symptoms, you should consult an allergist. It is important to differentiate between allergy and intolerance in order to determine the most appropriate further steps.

An immunological response usually occurs when the body perceives a particular substance as foreign. However, in most cases, the exact trigger cannot be identified, as there are several potential causes at once.

For example, alcohol intolerance can develop when a person drinks a particular type of alcohol, which may contain certain allergens. In this case, it would make sense to conduct allergy testing, blood tests, skin tests, or an elimination diet during an allergic reaction to identify the cause.

Should People With Alcohol Intolerance Avoid Drinking Alcohol?

People with a true allergic reaction must give up alcohol, as allergic reactions can be very dangerous. If you have had anaphylaxis after drinking, consult an allergist to determine the cause. In the future, it is necessary to avoid alcoholic drinks, since the next attack may well be fatal.

People with enzyme deficiency problems, such as aldehyde dehydrogenase 2 deficiency, should carefully consider giving up or limiting alcohol consumption. By itself, this inconvenience does not lead to any particularly dangerous consequences, but there are reasons to take this condition seriously. In particular, studies have shown that people with aldehyde dehydrogenase 2 deficiency are at higher risk for health problems that are exacerbated by alcohol consumption.[6]

As a rule, the use of ethanol leads to the accumulation of large amounts of acetaldehyde in the body, which has a toxic effect. In addition, you should definitely consult a doctor if you have alcohol intolerance, as it may be another disease that requires treatment.

There is also a reason for alcohol intolerance that is associated with the intake of certain drugs. In such cases, it is necessary to consult a doctor to discuss alternative drugs. If you have alcohol intolerance and a desire to drink, it is necessary to seek medical help. This is especially important if you have developed alcohol dependence, sometimes called alcohol use disorder.