Food allergy
In veterinary medicine, allergic reactions to feed ingredients are referred to as feed allergy or feed allergy (also feed-induced atopic dermatitis ; English adverse food reaction ) . It thus corresponds to the food allergy in humans. The disease manifests itself primarily as a skin disease with itching , which can lead to severe skin changes through scratching and licking. Food allergies occur mainly in domestic dogs and cats . Diagnosis and treatment are possible through an exclusion diet, but this is time-consuming.
Occurrence and origin
Food allergies are quite common in dogs and cats. Their share in dogs with skin reactions is 12%. Animals of all races and age groups are affected, although the disease usually begins in the first year of life in dogs. A feed allergy to a feed can occur years after initially problem-free feeding.
The most common allergens are beef and dairy products, but pork, horse, poultry, fish, eggs, soy and wheat can also trigger allergic reactions. In addition to the main components in finished feed, additives such as stabilizers, antioxidants or moisturizers can also trigger allergies. In addition, allergens can only arise through remodeling in the organism. The allergens are heat-, acid- and protease- resistant proteins, mostly glycoproteins , with a size of ten to 70 kDa . But also smaller proteins ( haptens ) can lead to allergic reactions if they are bound to carrier proteins.
Food allergies must be distinguished from intolerance reactions that take place without the involvement of the immune system , such as lactose intolerance .
The exact cause of such allergic intolerance is not yet known. Disorders of the barrier function of the intestinal mucosa due to intestinal inflammation ( e.g. parvovirus ), intestinal parasites and early withdrawal can be predisposing . In a healthy intestine, allergens cannot normally pass through the intestinal wall. In addition, they are largely broken down by the enzymes in the digestive juice. When allergens come into contact with the intestinal wall, there is an immune response with the formation of immunoglobulin A (IgA). The resulting antigen-IgA complexes can be absorbed. As a rule, however, such substances are tolerated.
Food allergies are mostly type I reactions , but type III and type IV reactions can also occur. Type III reactions are responsible for gastrointestinal symptoms, which, however, only occur in around 15% (dog) to 30% (cat, → feline eosinophilic enteritis ) of cases of food allergy . Type IV reactions are responsible for the fact that the allergy can persist for weeks even if the antigen is eliminated. How and why the food allergens get into the skin and trigger a reaction is still unclear.
Clinical picture
The clinical picture of food allergy is mainly characterized by skin inflammation (allergic dermatitis ) with itching . The first skin changes ( primary lesions ) are reddened skin ( erythema ) and papules in around 40 percent of cases . Preferred locations in dogs are paws , armpits , stomach , groin , muzzle and ears , in cats the head and neck. The ears are involved in 80% of the dogs, in 20% of the food allergy sufferers only the ears are affected. The various pictures of the eosinophil granuloma complex can appear in cats .
As a result of self-traumatization, pyotraumatic dermatitis or malassezia dermatitis can occur, which lead to secondary skin changes.
Diagnosis and treatment
All skin diseases associated with pruritus must be excluded from the differential diagnosis. In around 25 percent of cases, there is a second allergy ( atopic dermatitis of the dog , flea allergy ), which makes diagnosis even more difficult. The food allergy usually responds only slightly to glucocorticoids and does not usually occur seasonally.
The informative value of serological tests against food allergens is controversial, their sensitivity and specificity is low. Also intracutaneous have little significance. A newly developed test in which raw and cooked proteins are stuck to the skin in small aluminum chambers (patch test) has no informative value in the event of a positive reaction, but a negative reaction can help in choosing suitable components for the exclusion diet.
If a food allergy is suspected, a consistent exclusion diet is the diagnostic method of choice. The feeding is consequently switched to only one protein and carbohydrate source for at least six weeks. Choose a type of meat and a cereal product / potato that was not included in the previously used feed. It is imperative to avoid all supplementary feed with other protein and carbohydrate sources ("treats"). When choosing the exclusion diet, it should be noted that there are cross-allergies. The beef allergen Bos d 7 , which is most frequently involved in dogs, shows cross-reactions with the meat of other ruminants (sheep, game) and milk. Many of the ready-made feeds based on exotic proteins and carbohydrates that are now available in the free trade contain traces of common allergy triggers (soy, beef, poultry, rice), although they are not declared on the packaging.
After the diagnosis has been confirmed by an exclusion diet, the diet can be gradually expanded to include a further component every two weeks. In more than 90% of the food allergy sufferers, a new reaction occurs within 3 days, but in around 2% it can take 14 days before the typical symptoms recur. If it occurs again, the component is considered identified, although it must be noted that several feed components can also trigger allergies.
In cases with allergic reactions to many animal proteins, a special diet feed may have to be used. In these, the proteins are broken down to molecular sizes below the critical size (→ hydrolysis ).
Literature and Sources
- B. Bigler: Food allergy . In: PF Suter and B. Kohn (eds.): Internship at the dog clinic . Parey, 10th ed. 2006, ISBN 3-8304-4141-X , p. 372.
- W. Drochner: Food allergies . In: PF Suter and B. Kohn (eds.): Internship at the dog clinic . Parey, 10th ed. 2006, ISBN 3-8304-4141-X , p. 33.
- Ch. Noli and F. Scarampella: Feed allergy . In: Practical Dermatology in Dogs and Cats. Schlütersche Verlagsanstalt, 2nd edition 2005, ISBN 3-87706-713-1 , pp. 259-263.
Individual evidence
- ↑ a b Sandra Schröer and Ralf S. Müller: Diagnosis of food intolerance in dogs and cats . In: Prakt. Tierarzt 97 (2016), pp. 496–500.
- ↑ a b c A. Verlinden et al .: Food allergy in dogs and cats: a review. Crit Rev Food Sci Nutr. 2006; 46 (3): 259-73. PMID 16527756
- ↑ Stefanie Peters: Allergy - Part 2: "Food allergy" / Cutaneous adverse reactions to food components. In: Fachpraxis 33 (2009), pp. 10–7.
- ↑ a b c Regina Wagner: Food intolerance in dogs and cats. In: Veterinärspiegel 1/2012, pp. 15–20.
