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A recent review article discusses the difficulties in diagnosing allergies in children. Many of these difficulties also apply to horses, especially for the attempted diagnosis of food allergy. This article will summarize the authors’ guidelines for the interpretation of pediatric food allergy testing in human patients.

  • Food allergy may be suspected when specific signs (wheals, swelling, coughing, respiratory difficulty, or vomiting) occur minutes to hours after eating a certain food.
  • Skin prick tests and serum allergy tests are similar in their ability to rule in or rule out allergies.
  • It is common to have a positive reaction for a food that is tolerated without any ill effects.
  • It is advisable to not test for foods that are known to be well-tolerated by the patient.
  • Additional diagnostics for food allergy include an oral food challenge test.
  • A positive result without clinical allergy is common. For example, about 8% of patients may test positive for peanut allergy, but only about 1% are clinically allergic to peanuts.
  • A negative allergy result does not rule out food allergy. Different tests can have differing results. Using fresh food extracts for skin prick testing may increase the chances to confirm food allergy, especially for fruits.
  • Different food proteins can cross-react on allergy tests, which gives a much higher chance of a positive reaction. For example, greater than 50% of patients with peanut allergy test positive for other legumes, but less than 5% of patients have clinical signs of allergy if they eat these other legumes.
  • Allergens in food and inhaled allergens may also cross-react when there is no clinical allergy present. For example, birch pollen may cross-react with hazelnut, peanut, or soy. Grass pollen may give a false positive reaction for wheat or peanuts.
  • Skin prick or serum allergy tests do not predict the severity of a possible allergy, but they can reflect the likelihood of some type of allergic reaction to a given allergen.

While concrete conclusions cannot be drawn between human and equine allergy testing, this paper emphasizes the difficulty in definitively diagnosing food allergy. Ultimately, food allergy must be diagnosed when clinical signs of allergy disappear when the food is not fed and they reappear soon after the food is reintroduced into the diet (challenge test). The biggest dilemmas with any allergy test are that normal (nonallergic) horses will have positive reactions and that the allergen that is causing problems may not be included in the test.

Summarized from: Sicherer, S.H., and R.A. Wood. 2012. Allergy testing in childhood: Using allergen-specific IgE tests. Pediatrics 129:193-197.

Further reading on Equinews.com: Food Allergy in Horses.

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