What Is MSG? 

MSG is a sodium salt derived from glutamic acid, an amino acid that naturally occurs in many foods (like parmesan cheese and tomatoes).

This white, odorless crystalline powder has been used as a flavor enhancer for more than a century. It’s responsible for the “umami” or savory flavor in many dishes. It was originally made from boiled seaweed. Today, it is made by fermenting starch, sugar beets, sugar cane, or molasses.

While the Food and Drug Administration (FDA) says MSG is “generally recognized as safe,” its use remains controversial. Likely due to the uncomfortable symptoms people report experiencing after eating foods containing MSG.

The Symptoms of MSG Symptom Complex

MSG symptom complex is a cluster of adverse reactions often mistaken for a food allergy. It is not a true allergy, but rather a food intolerance.

Most people who have the syndrome experience mild and short-lasting symptoms after consuming MSG. These may include

Muscle pains Heart palpitations Facial pressure Headaches Nausea Flushing Tingling Chest heaviness Numbness on the back of the neck, shoulders, and arms 

Headaches

While research into MSG symptom complex is limited, there have been several reports of people experiencing headaches after consuming MSG. Studies suggest the food additive may have a connection to headaches.

Although the mechanism isn’t entirely understood, research has found people with migraines and tension-type headaches have higher levels of glutamate than those without migraines. While this does not confirm a causal link between migraines and MSG, it may help to explain the phenomenon of headaches after consuming MSG.

In addition, research shows MSG consumption can cause blood pressure to rise, which is linked to headaches. However, in studies, this increase has been short-lived and only occurs following MSG intake that is much higher than what is normally consumed in a meal.

Asthma

Research in the 1980s found a suspected link between MSG and asthma. In a small study published in the Journal of Allergy and Clinical Immunology, 32 people with asthma were put on an additive-free diet for five days, then given increasing doses of 500 mg to 5 grams of MSG in a hospital setting.

The MSG challenge provoked reactions in 13 people, with six experiencing symptoms of asthma and MSG symptom complex within two hours of ingestion, and another seven experiencing asthma flare-ups within 12 hours. These results, however, have not been replicated in further studies. 

A 1999 study of 100 people with asthma found no indication that MSG provokes asthma attacks based on diagnostic markers, including forced expiratory volume (FEV1) values.

In the study, people with asthma—with and without a history of self-diagnosed MSG symptom complex—were given 2,500 milligrams of MSG. Researchers found no clinically relevant changes in FEV1 levels and advised maintaining a “healthy skepticism about the existence of MSG sensitivity in individuals with asthma.”

Causes

MSG symptom complex is not very well understood. The reactions people experience after eating MSG do not involve traditional allergy pathways that activate an immune response.

Furthermore, despite widespread anecdotal evidence that some people experience reactions, studies of MSG have not demonstrated a clear cause-and-effect relationship.

Instead, only a handful of studies have found mild reactions can occur after consuming large amounts of MSG, and the threshold for symptom development is far above what would be consumed during a normal meal.

Diagnosis

MSG symptom complex is typically diagnosed based on symptoms that appear following MSG consumption. Your healthcare provider may ask questions such as:

Have you eaten food prepared with MSG within the past two hours?Have you eaten any other food that may contain monosodium glutamate within the past two hours?

He or she may also perform diagnostic tests, such as an electrocardiogram to check for abnormal heart rhythms and spirometry to test airflow.

Treatment

There is no specific treatment for MSG symptom complex, although over-the-counter medications can be used to treat individual symptoms during an episode. For example, Tylenol (acetaminophen) or Excedrin (aspirin, acetaminophen, and caffeine) may ease a headache.

More serious symptoms may be life-threatening and require immediate medical attention. Although MSG isn’t known to cause anaphylaxis, it’s possible a person may be allergic to a food that contains it.

Get emergency medical help right away if you experience any of the following, as they can be indications of life-threatening allergic reactions known as anaphylaxis:

Chest heavinessHeart palpitationsShortness of breathSwelling of the lips or throat

Avoiding MSG

The most effective strategy for avoiding symptoms is to not consume MSG if you suspect you may be sensitive to it. While there is little scientific evidence to support a link between MSG and reactions, the FDA requires food labels to list MSG as an ingredient.

Foods that naturally contain MSG do not need to list MSG as an ingredient, although the product label cannot claim “No MSG” or “No added MSG.“

Dining out while avoiding MSG can be trickier. You can always ask if the meal is prepared with MSG, and many restaurants now advertise they are MSG-free.

Monosodium glutamate Hydrolyzed vegetable proteinAutolyzed yeastHydrolyzed yeastYeast extractSoy extractsProtein isolateTomatoes Cheese

A Word From Verywell

Despite the belief that there is such a thing as an MSG allergy, there is a lack of hard scientific data to link common reported reactions to MSG. That said, sometimes misconceptions exist for a reason, and there may be some truth underlying the MSG phenomenon that experts simply have not yet figured out.

If you suspect foods containing MSG give you a headache or other unpleasant symptoms, by all means, avoid them.