What Is a Citrus Allergy and How Is It Diagnosed?

A citrus allergy is a reaction to the acid found in citrus fruits like oranges, limes, and lemons. It is not a true allergy but a sensitivity. Citric acid is a simple molecule, and the body doesn't produce an antibody to it that would trigger an allergic reaction or show up in a traditional allergy skin test.

Sensitivity to citric acid is uncommon, but some people do have allergy-like symptoms after eating citrus fruit.

This article examines citrus allergy, its causes, symptoms, and diagnosis. It also looks at some of the ways citrus allergy can be treated.

Causes 

Citrus allergy can have several different causes. Some people may be sensitive to eating citrus fruits, while others may react when touching the peels.

Cross-Reactivity

Some people who are sensitive to citrus have a condition called oral allergy syndrome (OAS). This condition causes you to react to proteins in food that are similar to the proteins found in pollens you are allergic to. This is known as cross-reactivity.

People who are allergic to grasses, in particular, may experience OAS to citrus fruits. A 2013 study, for example, found that 39% of study participants with confirmed pollen allergies were also sensitive to citrus.

Limonene allergy

Limonene is a chemical present in citrus peels. Some people have a contact allergy to limonene and may develop a rash after touching a citrus peel. It is possible to be allergic to limonene but not to the fruit itself.

Limonene is sometimes used commercially as a fragrance. If you react to citrus peels, it is a good idea also to avoid products that contain limonene.

Systemic Allergy

It is possible to have a serious, life-threatening allergic reaction to citrus fruits. Seek medical attention right away if you have symptoms of anaphylaxis, including:

• Trouble breathing
• Swelling of the throat and mouth
• A drop in blood pressure
• Nausea and vomiting
• Confusion
• Flushing of the skin

Symptoms

You can experience symptoms that aren't associated with an allergy after eating citrus fruit:

• Mouth sores
• Heartburn
• Aggravation of acid reflux symptoms

You might be having a food allergy reaction if you have the following symptoms:

• Itching of the mouth, tongue, and lips
• Rashes around the mouth
• Gastrointestinal symptoms, such as abdominal pain, bloating, or diarrhea
• Swelling of the mouth or throat
• Headaches
• Other symptoms of food allergy

Many different types of food can trigger these symptoms, but they are not usually part of sensitivity to citric acid.

Sources

Citric acid derived from natural sources has been used as a food additive for over 100 years. It's often used to provide a sour or tart flavoring, as a preservative, or as an emulsifier. It's also commonly added to canned and jarred foods to prevent botulism.

Citric acid is found in foods including:

• Ice cream
• Sorbet
• Caramel
• Soda
• Beer
• Wine
• Baked goods
• Processed sweets
• Pre-cut pre-packaged fruits and vegetables

Citric acid in its natural form is extracted from fruits. People who react to fruit-derived citric acid are allergic to the fruit, not citric acid itself.

Citric acid can also be synthesized commercially. If you're sensitive to the fruit or substances from this process, those may be what's triggering your reaction.

Mold or Corn Allergy

Citric acid can be synthetically produced using a type of mold called Aspergillus niger, a safe strain of black mold. It's much cheaper to produce it this way than to use the natural version.

In the manufacturing process, the mold culture is fed sugar solutions, which are often derived from corn. This is often the source of citric acid used as a food additive in many processed foods.

It's not unusual to have an allergy or a sensitivity to mold or corn, and in fact, many people who react to foods containing citric acid may actually be allergic to the mold or the corn used to produce the acid.

• If you have an allergy or sensitivity to airborne mold or mold found in the environment, you may also react to mold in or on the foods you eat.
• If you're allergic to corn, you may be sensitive to the tiny amount of corn that's left in citric acid during the manufacturing process.

An allergist can determine if you have an allergy to mold or corn by using a skin-prick test, but to determine if you're also sensitive to mold in foods, you'll need to do an elimination diet and supervised oral food challenge.

Diagnosis

Your healthcare provider may want you to try an elimination test to diagnose citrus sensitivity. During this test, you eliminate citrus fruits from your diet for two weeks, then you gradually add them back to see if you react. 

You can also be diagnosed with a supervised food challenge. This test is done in your healthcare provider's office. You are exposed to citrus under medical supervision during the test and are watched for an allergic reaction.

Treatment

The best way to treat a citrus sensitivity is to avoid citrus fruits. You will also need to avoid products that contain citrus.

People who experience severe reactions and are at risk of anaphylaxis should carry an EpiPen (epinephrine). It is important to keep your EpiPen with you at all times in case you experience a severe allergic reaction.

If your allergy is mild, you can try taking antihistamines. This may help reduce symptoms like itching in the mouth. If you have a skin allergy, topical cortisone can also help. 

When to See a Doctor

You should see a healthcare provider any time you have an allergic reaction, even a mild one. It is important to undergo testing to know what you are allergic to and what foods you need to avoid.

Summary

Citrus allergy is not a true allergy but rather a sensitivity to components of citrus fruit. Some people are sensitive to citrus because it contains proteins similar to those in airborne pollens. It is also possible to be allergic to the chemical found in citrus peels.

Most people sensitive to citrus have a mild reaction, but it is also possible to have a life-threatening anaphylactic reaction. If this happens, seek medical care at once.

An allergist can confirm whether or not you are sensitive to citrus. If you are, it's best to avoid citrus fruits and products that contain citric acid.

A Word From Verywell

Citric acid itself doesn't cause allergic reactions, but you may be sensitive to other components of citrus fruits.  

Even if your reaction is mild, such as itching inside your mouth, you should ask a healthcare provider about allergy testing. Any allergic reaction can be dangerous, and it is possible your response was caused by something other than citrus. Testing can confirm what you are sensitive to so you will know what to avoid in the future.