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Creature Companion 2014; December: 54-55.
Anton C. Beynen
Hypoallergenic petfoods
The term hypoallergenic in petfood labels relates to management of food allergy. True food
allergy is uncommon in the general population of dogs and cats. In the marketplace, on the other
hand, hypoallergenic foods are ubiquitous. This in itself is fine as well-formulated, complete and
balanced hypoallergenic dog or cat foods provide good nutrition.
Perceived rather than true food allergy is common. The abundance of hypoallergenic foods results
from consumer demand and manufacturers going along. Food is often blamed for signs such as
itching and diarrhea, leading to the self-diagnosis of food allergy. This conclusion may be
reinforced by disappearing of signs after switching the animal to a hypoallergenic food.
Understandably, the owner repurchases the brand. It is noteworthy that skin or gut problems may
improve after diet change because of spontaneous recovery, shift in season or associated
interventions.
Hypoallergenic foods can be prescribed and sold by veterinarians. Food allergy can only be
diagnosed by so-called elimination and provocation feeding tests. If the commercial,
hypoallergenic, elimination food is associated with improvement, many owners choose to continue
feeding the food without diagnosis. Blood testing for food allergy entails a high risk of a false-
positive outcome. Prescribed hypoallergenic foods may be followed on by resembling products
found in retail because of price and convenience. Thus, veterinary consultation tends to pave the
way for hypoallergenic foods overall.
The dictionary defines hypoallergenic as having little likelihood of causing an allergenic response.
The term hypoallergenic is ambiguous as it has no legal definition and no defined measure for
efficacy. EU legislation allows therapeutic petfoods with the purpose of reduction of certain
ingredient and nutrient intolerances. These foods, which are often labeled hypoallergenic, must
contain selected protein and/or carbohydrate source(s).
Food allergy
Food allergy is an individually-determined, immune-mediated reaction to a food component, which
generally is a protein source. The major, non-specific clinical sign is itching (pruritus), which leads to
scratching, licking and skin lesions. Diarrhea and vomiting occur less frequently. Dietary components
can also elicit the symptoms by non-immune mechanisms; this is called food intolerance. In popular
speech, it is joined under food allergy. Food allergy and intolerance are non-seasonal diseases
commonly referred to as adverse reactions to food. Therapy consists of avoiding the offending food
component(s).
Published case studies in dogs indicate that about 65% of adverse reactions relate to beef, dairy
products or wheat and 25% to lamb, soy, chicken or chicken egg (1). In cats, beef, dairy products and
fish are associated with almost 90% of the cases (1). These figures are inflated by the common use of
the incriminating protein sources as petfood ingredients. In dogs with non-seasonal pruritis entering
veterinary practice, adverse food reactions may account for about 20% of the cases (2). A rough
calculation suggests that the prevalence of true food allergy and intolerance in the general canine
population may be only 0.05%.
Diagnosis
Diagnosis of adverse food reactions by the veterinarian is based on multiple assessments. Dietary
investigation on individual dogs, in the form of elimination diets and test meals, is the decisive
diagnostic tool. Classically, elimination diets are not nutritionally complete and contain one protein
source that is novel to the patient and one starch-rich ingredient. If food sensitivity causes the
pruritis and/or diarrhea, the elimination diet induces amelioration, provided the animal is not
sensitive to it. There is relapse after provocation with the original food. Results of challenge tests
with individual dietary items can point to an appropriate, complete, commercial food. Alternatively,
a tolerable food, either labeled as hypoallergenic or not, can be identified by trying out.
Principles and practice
The formulation of hypoallergenic foods follows three principles. The number of (protein-containing)
ingredients is limited, novel protein sources are used and/or substances known to cause allergic
reactions are avoided. It is assumed that pets have not eaten novel proteins before and thus cannot
have developed an immune response to them.
Some petfood lines are all hypoallergenic, but most lines have one or more products so labeled. The
word sensitive may be used as synonym of hypoallergenic. Novel-protein diets or treats may contain
remarkable ingredients. The phrase limited- ingredient diets is commonly used. It even is part of a
brand name.
The ingredient lists of commercial hypoallergenic diets typically document between 2 and 6 protein-
containing ingredients. The degree of novelty of protein sources in many products is debatable. The
manufacturing process of hypoallergenic foods should exclude contamination with undesired
components. However, studies show that hypoallergenic dry foods, including therapeutic diets, may
contain protein sources not declared on the label (3, 4).
Hydrolytic breakdown of proteins into sufficiently small fragments lowers the chance of immune
recognition by patients that are allergic to the intact protein. Dogs with clinical sensitivity to soy
were less severe responsive to the protein sources in hydrolysate form (5, 6). Hydrolysed proteins
are expensive and only used in veterinary products recommended as both elimination and
hypoallergenic diets. These foods may have label descriptors such as low allergen, ultra allergen-free
and anallergenic.
Efficacy
The efficacy of a given hypoallergenic food cannot be predicted. Stricter implementation of
principles will increase the beneficial effect in pets on a group-mean basis. In five studies (7-11), on
average 48 % of dogs with true food sensitivity showed a favorable response to a commercial,
hypoallergenic food containing intact proteins. A hydrolysate-based, limited-ingredient food could
produce a better group-mean effect. Trial-and-error is still required to identify an appropriate food
for a dog with food sensitivity.
Literature
1. Roudebush P, Guilford WG, Shanley KJ. Adverse reactions to food. In: Small Animal Clinical
Nutrition, 4th Edition (Hand HS, Thatcher CD, Remillard RL, Roudebush P, eds), Mark Morris
Institute, Topeka, Kansas, 2000, pp 431-453.
2. Chesney CJ. Systematic review of evidence for the prevalence of food sensitivity in dogs. Vet Rec
2001; 148: 445-448.
3. Raditic DM, Remillard RL, Tater KC. ELISA testing for common food antigens in four dry dog foods
used in elimination trials. J Anim Physiol Anim Nutr 2011; 95: 90-97.
4. Ricci R, Granato A, Vascellari M, Boscarato M, Palagiano C, Andrighetto I, Diez M, Mutinelli F.
Identification of undeclared sources of animal origin in canine dry foods used in dietary elimination
trials. J Anim Physiol Anim Nutr 2013; 97: 32-38.
5. Jackson HA, Jackson MW, Coblentz L, Hammerberg B. Evaluation of the clinical and allergen
specific serum immunoglobulin E responses to oral challenge with cornstarch, corn, soy and a soy
hydrolysate diet in dogs with spontaneous food allergy. Vet Dermatol 2013; 14: 181-187.
6. Puigdemont A, Brazis P, Serra M, Fondati A. Immunologic responses against hydrolyzed soy
protein in dogs with experimentally induced soy hypersensitivity. Am J Vet Res 2006; 67: 484-488.
7. White SD. Food hypersensitivity in 30 dogs. J Am Vet Med Assoc 1986; 188: 695-698.
8. Jeffers JG, Shanley KJ, Meyer EK. Diagnostic testing of dogs for food hypersensitivity. J Am Vet
Med Assoc 1991; 198: 245-250.
9. Rosser Jr EJ. Diagnosis of food allergy in dogs. J Am Vet Med Assoc 1993; 203: 259-262.
10. Vroom MW. Prospectief onderzoek van een commercieel hypoallergeen dieet bij achttien
honden met een voedselallergie. Tijdschr Diergeneeskd 1994; 119: 602-604.
11. Leistra MH, Markwell PJ, Willemse T. Evaluation of selected-protein-source diets for
management of dogs with adverse reactions to foods. J Am Vet Med Assoc 2001; 219: 1411-1414.