Food al­lergy or sen­si­tiv­ity? How to find out

The Morning Call - - HEALTH - By Cara Rosen­bloom

If you are deal­ing with symp­toms such as hives or bloat­ing, you may sus­pect a food al­lergy or sen­si­tiv­ity. But how can you de­ter­mine which foods are caus­ing the re­ac­tions? There are so many food al­lergy and sen­si­tiv­ity tests avail­able, it can be dif­fi­cult to fig­ure out where to start. But with the right meth­ods and doc­tor in­volved, you can of­ten zero in on the prob­lem.

If you search on­line for “food al­lergy test­ing,” you’ll find op­tions in­clud­ing clin­i­cal vis­its with al­ler­gists and im­mu­nol­o­gists and do-it-your­self test kits that claim to de­liver com­pre­hen­sive re­sults (with a 100 per­cent money-back guar­an­tee!). Not all of the meth­ods are equally re­li­able, and some are down­right fraud­u­lent. There is no sin­gle test that will tell you ex­actly which foods to avoid. If a web­site, ad­ver­tise­ment or prac­ti­tioner claims to pro­vide such a test, watch out. Take these steps in­stead.

Al­lergy or sen­si­tiv­ity?

It’s im­por­tant to know the dif­fer­ence be­tween a food al­lergy and a food sen­si­tiv­ity. Although the terms are of­ten used in­ter­change­ably and symp­toms may over­lap, they are not the same. A food al­lergy is an im­mune sys­tem re­ac­tion that can cause hives, wheez­ing, itch­ing, di­ar­rhea, vom­it­ing, short­ness of breath and ana­phy­laxis. About 3.6 per­cent of Amer­i­cans have food al­ler­gies, says a 2017 Brigham and Women’s Hos­pi­tal study.

Food sen­si­tiv­ity (some­times called food in­tol­er­ance) is a re­ac­tion that in­volves the di­ges­tive sys­tem, not the im­mune sys­tem. Symp­toms in­clude gas, bloat­ing, nau­sea, vom­it­ing and di­ar­rhea. Although in­tol­er­ances can be painful and un­com­fort­able, they are not life-threat­en­ing, and are rarely as se­ri­ous as true food al­ler­gies. Any­where from 2 to 20 per­cent of Amer­i­cans may be sen­si­tive to cer­tain foods — there are no pre­cise num­bers be­cause there is no ex­act di­ag­nos­tic test.

For food al­lergy

If you sus­pect a food al­lergy, don’t self­di­ag­nose or use at-home test kits. Food al­ler­gies are much too se­ri­ous to as­sess with­out an ex­pert. Your best bet is to work with a board-cer­ti­fied al­ler­gist, who will per­form skin-prick tests and IgE blood tests to nar­row down a di­ag­no­sis. (IgE, or im­munoglob­u­lin E, is an an­ti­body pro­duced by the im­mune sys­tem. More IgE is pro­duced dur­ing an al­ler­gic re­ac­tion.) Keep in mind even these tests are im­per­fect, and may falsely show you are al­ler­gic to some­thing.

“Both skin and blood IgE tests have high rates of false pos­i­tive re­sults and, be­cause of this, they should never be used as ‘screen­ing tests,’ ” says David Stukus, an al­ler­gist and as­so­ciate pro­fes­sor in the divi­sion of Al­lergy and Im­munol­ogy at Na­tion­wide Chil­dren’s Hos­pi­tal in Ohio. “Both skin-prick and blood test re­sults must be in­ter­preted in the proper clin­i­cal con­text and with a full un­der­stand­ing of what symp­toms oc­cur when that food is in­gested. Both are re­li­able when used ap­pro­pri­ately and in­ter­preted in the proper con­text.”

You may hear al­ter­na­tive prac­ti­tion­ers talk about di­ag­nos­ing food al­ler­gies with other tests such as hair anal­y­sis, IgG tests (which mea­sure im­munoglob­u­lin G, an­other an­ti­body pro­duced by the im­mune sys­tem), fa­cial ther­mog­ra­phy and mus­cle test­ing. It’s im­por­tant to note that the Na­tional In­sti­tute of Al­lergy and In­fec­tious Dis­eases’ Guide­lines for the Di­ag­no­sis and Man­age­ment of Food Al­lergy in the United States says these tests “lack ev­i­dence demon­strat­ing any value in di­ag­nos­ing food al­ler­gies.” They also can set you back a few hun­dred dol­lars each, and you might en­dan­ger your health with in­ac­cu­rate re­sults.

The gold-stan­dard food al­lergy test is an oral food chal­lenge done in part­ner­ship with your al­ler­gist, which may be done in con­junc­tion with IgE and skin-prick tests. For an oral food chal­lenge, you will eat small amounts of the sus­pected al­ler­gen and watch for a re­ac­tion in the safety of the doc­tor’s of­fice (with an­ti­his­tamines and ep­i­neph­rine on hand in case of se­ri­ous re­ac­tions).

“Di­ag­nos­ing food al­ler­gies is com­pli­cated and re­quires some­one with proper train­ing to ob­tain a de­tailed clin­i­cal his­tory and in­ter­pret test re­sults,” Stukus says. “Self­di­ag­nos­ing food al­lergy with home test­ing is filled with pit­falls and of­ten leads to mis­di­ag­no­sis and un­nec­es­sary food elim­i­na­tion. It also runs the risk of miss­ing other con­di­tions or fac­tors that may have been the true cause of symp­toms.”

For food sen­si­tiv­ity

Un­for­tu­nately, there are no val­i­dated tests to di­ag­nose food sen­si­tiv­ity, even though mar­ket­ing leads con­sumers to think many test meth­ods are ac­cu­rate and re­li­able. Don’t be­lieve the hype.

Most of the ex­cite­ment sur­rounds the IgG test (again, dif­fer­ent from the IgE blood test), which is mar­keted as a way to iden­tify hid­den food sen­si­tiv­i­ties or in­tol­er­ances. Stukus says this is not an ev­i­dence-based rec­om­men­da­tion, and the IgG test is more likely to in­di­cate the foods you com­monly eat, not the ones caus­ing you an is­sue. Stud­ies show that IgG can be a marker of ex­po­sure to food and pos­si­bly of tol­er­ance — the op­po­site of sen­si­tiv­ity.

If you sus­pect a food sen­si­tiv­ity, an elim­i­na­tion diet is the most re­li­able way to de­ter­mine your trig­ger foods. In con­sul­ta­tion with your doc­tor or di­eti­tian, you will re­move foods from your diet that you sus­pect are caus­ing re­ac­tions such as gas and bloat­ing. You will later rein­tro­duce the foods one at a time, and keep track of symp­toms to see which foods cause a re­ac­tion. And hey, no fancy kits to buy — re­gard­less of the mon­ey­back guar­an­tee.

Rosen­bloom, a reg­is­tered di­eti­tian, is pres­i­dent of Words to Eat By, a nutri­tion com­mu­ni­ca­tions com­pany spe­cial­iz­ing in writ­ing, nutri­tion ed­u­ca­tion and recipe devel­op­ment. She is the co-au­thor of “Nour­ish: Whole Food Recipes Fea­tur­ing Seeds, Nuts and Beans.”

ESKEMAR/GETTY IM­AGES

It’s im­por­tant to know the dif­fer­ence be­tween a food al­lergy and a food sen­si­tiv­ity. Although the terms are of­ten used in­ter­change­ably and symp­toms may over­lap, they are not the same.

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