Understanding dog adverse food reactions It    is    not    uncommon    in    clinical    routine,    to    see    dogs    presenting    signs    of    food    adverse    reactions.    Unspecific dermatological   and   gastrointestinal   symptoms   are   reported,   including   red   inflamed   skin,   scratching   and   hair   loss, flatulence,   vomiting   and   diarrhoea,   poor   growth   in   young   pets,   etc.   The   diagnosis   involve   the   collection   of   an accurate    feeding    history    and    dog’s    environment    and    the    screening    for    some    diseases    trough    complementary examinations, if needed. Between   10   to   20%   of   skin   diseases   may   be   caused   by   food   allergy,   placing   this   condition   thirdly,   right   after   flea allergy,   in   the   rank   of   skin   allergies.   However,   there   is   an   indiscriminately   use   of   the   term   food   allergy,   which requires further clarification. An   adverse   food   reaction   may   be   either   immunologic   (food   allergy)   or   non-immunologic   (food   intolerance).   Food intolerance   is   subdivided   in   idiosyncrasy,   poisoning/intoxication   and   food   metabolic   reaction.   The   following   table presents some examples of food intolerance: Metabolic   reactions   are   related   to   the   individual,   and   can   be   due   to   a   health   condition,   malnutrition,   congenital   or acquired   errors   of   metabolism,   etc.   It   may   also   be   due   to   disaccharides'   intolerance   that   results   from   an   abrupt change   of   food   to   which   some   dogs   are   particularly   sensitive.   While   the   other   two   are   usually   a   consequence   of dietary   indiscretion   or   a   response   to   specific   foods   (e.g.   chocolate),   foods   contaminated   with   microorganisms   or other   toxic   metabolites   (toxins).   The   signs   are   mainly   gastrointestinal,   including   vomiting,   diarrhoea,   intermittent abdominal   pain   and   distention,   excessive   flatulence,   increased   frequency   of   defecation   and   soft   faeces,   with   no predisposition of age, sex or breed. Food   allergy   is   an   immunologic   reaction,   defined   as   an   aberrant   adverse   response   to   a   specific   food   substance (allergen).   It   differs   from   the   previous   because   it   is   characterized   by   the   existence   of   a   hypersensitivity   reaction, likely   involving   type   I   (Ig-E   mediated),   type   III   (mediated   by   the   immune   complex)   and/or   type   IV   (cell   mediated). Although   there   is   no   sex   or   age   predilection   for   food   hypersensitivity,   many   of   the   cases   seen   in   the   clinical   routine occur   in   dogs   with   less   than   1   year,   when   they   are   first   exposed   to   foods.   The   symptoms   are   non-seasonal   pruritic dermatitis,   accompanied   or   not   by   gastrointestinal   signs.   The   cutaneous   symptoms   may   mimic   another   allergic dermatosis   such   as   atopy   (characterized   by   lesions   with   ventral   distribution,   in   the   extremities,   ears   and   face). Nevertheless,   the   pruritus   caused   by   food   allergy   occurs   most   often   in   the   ears   and   perianal   area   as   a   consequence   of licking.    In    dogs    with    less    than    six    months,    cutaneous    manifestations    of    food    allergy,    are    more    common    than environmental allergies. It may be distinguished from the last ones since these are usually seasonal. Food   allergens   are   mainly   glycoproteins   with   a   minimum   molecular   weight,   capable   of   triggering   the   immunity response   (10   to   70   kDa).   The   most   often   reported   allergen   sources   are   beef,   dairy   products,   chicken,   wheat   and lamb.   Other   less   frequently   reported   include   soy,   corn,   egg,   pork,   fish   and   rice,   etc.   This   type   of   reaction   may   be similar   to   an   idiosyncrasy,   as   is   the   case   of   the   allergic   reaction   to   milk   proteins   (e.g.   bovine   IgG)   that   can   mimic carbohydrate   intolerance.   In   this   particular   case,   withdrawing   milk   from   the   diet   will   solve   the   problem. Actually,   the strategy   for   treating   adverse   food   reactions   is   to   avoid   the   exposition   to   certain   foods.   However,   in   most   of   the   food allergies   the   identification   of   allergen   sources   may   not   be   easy.   Diet   elimination   is   frequently   used   to   look   for   the source   of   allergy.   It   becomes   essential   to   owners   to   read   carefully   the   food   labels   (for   moist   and   dry   commercial diets)   in   order   to   identify   the   ingredient   composition.   Since   this   allergens   may   be   present   in   several   foods,   the solution   could   concern   to   feed   dogs   with   diets   containing   hydrolysed   proteins.   Hydrolysed   proteins   are   protein fragments   with   molecular   weight   below   the   10   kDa   that   have   lower   allergenicity   conferring   the   advantage   of   higher digestibility to the diet in which they are incorporated.

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