What Is Watermelon Allergy?

How Oral Allergy Syndrome Explains the Relationship

Watermelon slices on a blue picnic table

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Most people are familiar with hay fever and food allergies, but many do not realize there can be a connection. Many people with hay fever also experience allergic symptoms in or around the mouth after eating certain raw fruits and vegetables, including watermelon. This type of reaction is known as pollen food allergy syndrome, or oral allergy syndrome (OAS).

Technically, a watermelon allergy is OAS, which is different from a food allergy. Unlike with a food allergy, OAS symptoms aren't caused by food proteins. Instead, OAS is caused by pollen allergens that cross-react with certain plant foods, triggering the immune system to mount an allergic response.

This article explains watermelon allergy symptoms, diagnosis, and treatment. It also covers risk factors for developing a watermelon allergy and which foods to avoid if you develop OAS.

Symptoms of Watermelon Allergy

Unlike food allergies, which can cause many systemic (body-wide) symptoms, watermelon allergy caused by OAS usually only produces localized itching. Symptoms of OAS include:

  • Itchy mouth
  • Scratchy throat
  • Lips, mouth, tongue, throat swelling

People with OAS usually only experience a reaction when eating raw fruits or vegetables because cooking alters the proteins involved. These symptoms typically begin immediately after putting the watermelon in your mouth and go away soon after swallowing it.

Anaphylaxis

While rare with OAS, anaphylaxis, a severe, life-threatening allergic reaction, can occur with any allergy. So, if you experience any of the following symptoms of anaphylaxis, seek medical attention right away:

  • Hives
  • Swelling
  • Wheezing
  • Unconsciousness
  • Chest tightness
  • Difficulty breathing
  • Hoarseness
  • Trouble swallowing
  • Vomiting
  • Diarrhea
  • Stomach cramps
  • Flushing
  • A feeling of impending doom

How Is Watermelon Allergy Diagnosed?

A careful history can usually provide enough clues to a healthcare provider that OAS may be the culprit. However, some diagnostic tools can help them confirm their suspicion.

Allergy testing may include:

  • Skin test, where an allergist (an allergy specialist) scratches your skin with an allergen then watches for a reaction
  • Blood test, where a lab technician evaluates your blood for IgE antibodies
  • Oral food challenge, where you consume suspect foods and document any reaction

If you don't test positive for a specific food allergy, but you do test positive for grass or ragweed pollen, an allergist may diagnose a watermelon allergy.

Risk Factors for Watermelon Allergy

A ragweed allergy is associated with OAS reactions to watermelons. Though anyone can develop OAS, the condition is less common in young children.

What Causes Watermelon Allergy?

Certain foods correlate with particular environmental allergens. For example, if you are allergic to various types of melons, you may also experience allergic rhinitis (nasal allergies) caused by ragweed pollen.

OAS symptoms are your body reacting to the proteins in the fruit that resemble those in pollen. This cross-reactivity confuses the immune system, resulting in OAS symptoms.

Other common correlations include the following.

While the above associations are possible, they do not exist in every individual. For example, a person with birch pollen allergy may have OAS to apples but not react to any other foods mentioned. Similarly, a person may have a ragweed pollen allergy and only notice oral symptoms with melons.

Watermelon Allergy in Children and Babies

While less common in young children, older children, teens, and young adults may suddenly develop OAS even after eating watermelon for years without any issues.

A 2015 study published in the International Dental Journal evaluated the prevalence of OAS in children. In 120 kids with seasonal allergic rhinitis, OAS symptoms were most pronounced in those with a birch allergy.

In addition, OAS was more common in teens than older children and more prevalent in those with allergic rhinitis and asthma, and allergic rhinitis and eczema.

Recap

The most significant risk factor for watermelon allergy is a pollen allergy—especially grass and ragweed. OAS is most common in adults, but kids can also develop OAS. It is more common in adolescents than younger children.

Treatments for Watermelon Allergy

Because the symptoms are mild and fade quickly, treatment usually is not usually necessary.

How to Treat an Allergic Reaction to Watermelon

If you ever experience a severe allergic reaction, a healthcare provider will likely prescribe an EpiPen.

An EpiPen is a synthetic form of epinephrine hormone that you inject when you experience anaphylaxis. It can stop the allergic reaction and give you time to seek emergency medical care.

When To See a Healthcare Provider

If you experience symptoms of OAS, it's good to make an appointment with an allergist or your primary healthcare provider for a diagnosis. In addition, if you ever experience symptoms of anaphylaxis, like difficulty breathing, swelling, or hives, seek emergency medical care immediately.

Foods to Avoid

If you have a watermelon allergy brought on by OAS, you should avoid consuming watermelon. In addition to whole watermelon, keep an eye out for watermelon in salads, drinks, and smoothies.

People with OAS often have reactions to more than one food. So, if you have a ragweed allergy, you may also react when you eat these foods:

  • Banana
  • Cantelope
  • Chamomile
  • Cucumber
  • Echinacea
  • Honeydew
  • Sunflower seeds
  • Zucchini

If you notice a reaction to any other foods, add them to your list of foods to avoid.

Summary

Oral allergy syndrome causes a watermelon allergy. It happens when you have a pollen allergy that cross-reacts with specific proteins in some fruits and vegetables, including watermelon.

Symptoms are immediate and localized and include itching and tingling in the mouth and throat. Symptoms resolve quickly, usually on swallowing. Rarely anaphylaxis can occur. Treatment includes avoiding the offending food and using an EpiPen for severe reactions.

A Word From Verywell

If you have seasonal allergic rhinitis, you are at increased risk of OAS. However, not everyone with pollen allergies develops OAS. Remember that OAS can occur even after a lifetime of eating watermelon without a problem. So, if you suddenly develop symptoms, seek out a diagnosis. That way, you'll have a clear idea of managing the situation in the future.

Frequently Asked Questions

  • What's in watermelon that makes you allergic?

    When you have a watermelon allergy, your body is actually confusing the proteins in the melon that resemble those in pollen. This immune system mix-up is known as "cross-reactivity."

  • What is pollen-food allergy syndrome?

    Pollen-food allergy syndrome (PFAS) is another term for oral allergy syndrome (OAS). It means that when you have a pollen allergy, the protein in some plant foods can resemble those in pollen and confuse your immune system, resulting in localized OAS symptoms like itching when you eat certain foods.

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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