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The Causes and Signs of Strawberry Allergy

written by: J.Sace • edited by: Emma Lloyd • updated: 5/24/2011

Love strawberries, but can't eat them without triggering an allergic reaction? Did you know that the allergic property of the strawberry has to do with its beautiful red color? Read this article to find out why.

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    The Strawberry: A Sweet, Delicious 'False Fruit'

    Strawberries 

    The strawberry plant belongs to the rose family, Family Rosaceae. It belongs to the genus Fragaria and is widely cultivated in the temperate region. This low, perennial herb is popular for its sweet and reddish fruits. There are four principal species of strawberry in the world. These are the wood strawberry (Fragaria vesca), meadow strawberry (Fragaria virginiana), beach strawberry (Fragaria chiloensis), and the species from which most varieties came from, Fragaria moschata. The fruit of the strawberry is technically a “false” fruit because the seeds are located outside the fruit.

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    How do Strawberries Cause Allergies?

    Strawberries contain different kinds of proteins and some of these can trigger allergic reactions in humans. The human immune system mistakenly recognizes these proteins as harmful, so it initiates an allergic response, designed to protect the body. Your first exposure to strawberries may not trigger violent allergic symptoms, but it does set the stage for future reactions as your immune system is already producing immunoglobulin E (IgE) antibodies to neutralize the proteins and protect you on future exposure. If you are exposed to strawberries a second time, the IgE antibodies stimulate body cells to produce histamine. Histamine promotes blood vessel dilation, fluid secretion, and muscle spasm. There is still no reliable explanation as to why some people have a strawberry allergy, while others do not.

    Researchers from the University of Lund in Sweden announced that they have isolated a particular protein which may be the culprit for this allergic reaction. This protein is one, among others, that gives the fruit its beautiful red color. The researchers did not find that protein in white strawberries. In addition, the molecular structure of the allergen (the protein) in red strawberries was found to have  some similarities to that of the birch pollen allergen. So a person who is allergic to birch pollen may also be allergic to strawberries but not vice versa.

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    Signs of Strawberry Allergy

    Signs of strawberry allergy may include the following:

    •  Swelling of tongue, mouth, and throat
    •  Itchiness
    • Rashes
    • Hives
    • Watery eyes
    • Vomiting
    • Diarrhea
    • Anaphylactic shock

     

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    Testing

    Tests for strawberry allergy can be performed by a professional allergist. The allergist will perform a skin test, sometimes referred to as a 'scratch test'. He or she will scratch a needle with the allergen (strawberry substance) in a small portion of your skin. You are allergic to the fruit if after 15-30 minutes, a small bump surrounded by redness occurs on the skin. The bump is itchy and may continue to slightly grow. This allergic reaction indicates that your skin contains antibodies for the allergen contained in the strawberry. The formation of the bump and the redness occurred when histamine promoted blood dilation.

    Another test is by measuring the level of IgE antibodies in your blood. An increased IgE level may indicate that you are allergic to strawberry. However, this test is quite expensive and getting the test result may take some time. The skin test is proven to be more accurate, faster, and cheaper.

     

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    Managing

    Unfortunately for those who enjoy this delicious treat, the best way to avoid an allergic reaction is to avoid eating anything strawberry. Even processed strawberries (e.g. jam) should be avoided, as heat cannot alter or modify the allergens. Take time to check the food labels of prepared or processed foods to avoid any unpleasant surprises. The more severe your allergic reaction is, the more careful you will need to be to make sure strawberry has not been added to the food. Though the flavor is not quite as sweet as the red variety, if you are really craving strawberries, try the white variety, which you can safely eat as it does not contain the allergen.

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    References

    The Colour of Strawberry Allergy -- Royal Society of Chemistry; Advancing the Chemical Sciences

    Cowley, David. Strawberry Allergy Explained. Retrieved on March 27, 2009 from Helium.com

    Strawberry Allergies: Pick the White Ones Instead!. Retrieved on March 27, 2009 from Allergizer.com

    “Strawberry Allergy Symptoms” Retrieved on March 27, 2009 from TheBrightestHub.com

    Askenase, Philip W. "Allergy." Microsoft® Student 2008 [DVD]. Redmond, WA: Microsoft Corporation, 2007.

     

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    Photo Credit

    http://en.wikipedia.org/wiki/File:Strawberry3500px.jpg