diagnosis of food allergy and intolerance - vickerstaff ：食物过敏和不耐受诊断维克斯塔夫

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1、DiagnosisandDietaryManagementofFoodAllergiesandIntolerancesClinicalApplicationsTestsforAdverseReactionstoFoodsRationaleandLimitations3StandardAllergyTestsSkintestsScratchorprickAllergenextractappliedtoskinsurfaceofarmorbackSkinisscarified(scratched)orprickedwithlancetAllergenenc

2、ountersmastcellsbelowskinsurfaceIfallergen-specificIgEispresent,allergenplusantibodycausesreleaseofmediators(mastcelldegranulation),especiallyhistamineHistaminecausesreddeningandswelling:“whealandflare”reactionoftheskintestSizeofreactionmeasured(usually1+to4+)4StandardAllergyTests

3、SkintestscontinuedIntradermaltestsAllergenextractisinjectedintodermisRationale:releaseofhistamineproduceswhealandflareNote:manycountriesdonotapprovethistypeoftestingbecauseofincreasedriskofanaphylaxisasallergenintroduceddirectlyintobloodstreamControlsforallskintests:Negative:mediu

4、minwhichallergenissuspended(usuallysaline)Positive:measuredamountofhistamine5WhealandFlareReactionSkinpricktests6ValueofSkinTestsinPracticePositivepredictiveaccuracyofskintestsrarelyexceeds50%ManypractitionersratethemlowerNegativeskintestsdonotruleoutthepossibilityofnon-IgE-mediat

5、edreactionsDonotruleoutnon-immune-mediatedfoodintolerances7ValueofSkinTestsinPracticeTestsforhighlyallergenicfoodsthoughttohavecloseto100%negativepredictiveaccuracyfordiagnosisofIgE-mediatedreactionsSuchfoodsinclude:EggMilkFishWheatTreenutsPeanut8ReasonsforFalsePositiveSkinTe

6、stsDegranulationofskinmastcellsbystimulithatdonotdegranulatemastcellsinthedigestivetractDifferencesintheforminwhichthefoodisappliedtotheskincomparedtothatwhichencountersimmunecellsinthedigestivetractRawforminextractmaybedegradedduringcookingDigestionbygastricacidanddigestiveenzyme

7、scandegradeantigensAllergenextractcontainshistamine9FalseNegativeSkinTestsChildrenyoungerthan2-3yearsaremorelikelytohaveanegativeskintestandpositivefoodchallengethanadultsAdversereactionisnotmediatedbyIgECommercialallergenmaycontainnomaterialthattheimmunesystemcanrecognizeProcessi

8、ngoffoodleadstodegradationofaller