Food allergy:

Food allergy is a complex clinical disease in dogs and cats that is difficult to diagnose, treat, and avoid.

Food allergy can cause atopic dermatitis in dogs and can coexist with atopic syndrome in cats (feline atopy syndrome).

Principle and mechanism

Food allergy is the failure of the body's immune tolerance to food, resulting in immunoglobulin E (IgE) or Clinical disease consequences of non-IgE-mediated immune disorders.

Food allergy is not always a simple allergic reaction. It may be the result of food intolerance, toxins and pathogen attack at the same time, such as the proliferation of opportunistic pathogens Clostridium perfringens or roundworm infection .

Symptoms

Dogs: mostly urticaria, recurrent pyoderma, lower back itching

Cats: mostly urticaria, conjunctivitis, respiratory symptoms .

Both cats and dogs can have intestinal symptoms.

Otitis externa and otitis media may be the result of allergy symptoms.

Some dogs and cats exhibit allergic reactions to the environment.

The picture is from the reference literature, which shows that cats with food allergies achieve relief after dietary elimination

Allergens

The most common food allergens are 15-15 in size Between 40kDa (kDa is the unit of molecular weight).

Dogs: Beef, dairy, chicken and wheat are the most common allergens in dogs.

Cats: Chicken, beef and fish are the most common allergens in cats.

Known ingredients:

Specific allergens in beef: bovine serum albumin (Bos d6), phosphoglutaminase, bovine IgG (Bos d7);

Specific allergens in eggs: egg albumin (Gal d1), ovalbumin (Gal d2), ovotransferrin (Gal d3), allergy-specific IgE;

in fish Specific allergens: tropomyosin, enolase (Gad m2).

Cross-allergic reaction: A similar or incomplete cross-allergic reaction to a substance with a similar structure.

Research has confirmed the existence of serum IgE cross-reaction between chicken and fish;

Serum cross-reaction between poultry, ruminants, poultry and grains has also been further proved, with Allergic dogs and cats should have an accurate dietary history and avoid cross-eating after a dietary elimination experiment.

In human food allergies, pollen can cause allergies to food, known as pollen-food allergy syndrome (PFAS). Although there are no relevant studies in cats and dogs, food allergies in many dogs and cats are indeed seasonal, and sudden allergies to certain foods are prone to occur during pollen seasons.

Cross-allergic reactions can make food choices difficult, either to a completely new protein or to a combination of different food types.

Food allergies aside, a combination of plants and insects in the environment can also cause allergies in cats.

Diagnosis and Adjustment

Serum allergen IgE testing has come under considerable scrutiny due to a lack of consistency in its results, as well as a lack of consistency in clinical food selection results, which has been shown to Not reliable in predicting clinical allergy.

Similarly, serum IgG measurements or saliva tests for food-specific antibodies are unreliable.

Intradermal patch testing has good negative predictive value and is helpful in selecting proteins for dietary elimination experiments, but it is not practical because the allergen needs to be in contact with the skin for 48 hours and has a low positive predictive value. (That is, if the allergic reaction to a certain substance is tested negative, the reference value is high, and if it is positive, the reference value is low and the operation is inconvenient.)

Therefore, the dietary elimination test is currently the only method that can diagnose food allergy. . To put it simply, it means to eliminate foods that may cause allergies one by one

Dietary choices

When choosing foods, theoretically you should choose Never had access to sources of protein and carbohydrates before, but in reality, finding commercial food like this is very difficult. The use of insects as a novel protein source to manage food allergies has been proposed. Insects have highly digestible proteins.

However, insects may contain IgE specificities associated with storage mites and dust mites and are therefore not a reliable option for patients allergic to these substances.

In commercial foods, even single novel proteins are susceptible to contamination by other products. Since production lines usually produce more than one kind of food, different studies have proven that external contamination can be detected in 33%-83% of these foods through PCR, ELISA and other methods.

Therefore, the search for new proteins and cross-allergic reactions make food selection more complicated. Therefore, hydrolyzed proteins are often used instead of new protein selections. Proteins are usually hydrolyzed to a molecular weight of less than 5kDa, which is not easy in theory. Cause allergic symptoms.

Hydrolyzed foods usually contain carbohydrates, and cornstarch is less likely to cause allergies than corn flour.

One study conducted an experiment on 10 dogs allergic to chicken. The poultry feathers were hydrolyzed into a hydrolyzed diet with a molecular weight of less than 1kDa. The results showed that these dogs showed no clinical symptoms at all. However, if only part of the food is hydrolyzed, 40% of dogs will still develop a clinical reaction.

Choosing a home-cooked diet offers better protection against external contamination than a commercial diet, but ensuring nutritional balance can be difficult. However, under the guidance of a nutritionist, a homemade diet can be adjusted to meet nutritional needs

Dietary elimination experiment

After a food allergy is identified, a dietary elimination experiment can be started, using Single meat protein and single carbohydrate (if necessary) for at least 2 weeks.

If allergies occur midway, return to the new protein diet or hydrolyzed diet, and then transition to the next food to try.

85% of dogs will improve within 5 weeks after the dietary elimination experiment, and 95% of dogs will improve within 8 weeks; cats can achieve 80% improvement in 6 weeks , extending to 8 weeks can improve 90% of cats.

Intestinal symptoms often disappear earlier than skin symptoms.

The use of anti-inflammatory drugs can shorten the diet elimination experiment to 4-6 weeks. For example, after completely discontinuing prednisolone or Aibok, the itching does not reappear within two weeks.

Be cautious in interpreting relief and persistence of symptoms, especially when the cat suffers from both environmental and food allergies.

Considering that allergies may vary seasonally, environmental allergies are more likely to occur in summer, so dietary elimination experiments will be more efficient in winter.