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Skin Disease Due to Food Allergies in Dogs

Dermatologic Food Reactions in Dogs

Dermatologic food reactions in dogs are non-seasonal responses that occur when an animal consumes one or more substances in its food that trigger allergies. The primary physical manifestation of these reactions is often an intense itchiness, leading to excessive scratching of the skin.

Although the exact cause of these reactions is not fully understood, it is believed that both immediate and delayed responses to food result from a hypersensitive immune reaction. Conversely, food intolerance is a non-immunologic idiosyncratic reaction caused by the metabolic, toxic, or pharmacologic effects of the problematic ingredients. Since distinguishing between immunologic and idiosyncratic reactions is challenging, any negative response to food is generally termed as an adverse food reaction.


  • Itchiness not limited to specific body areas and occurs throughout the year
  • Poor response to anti-inflammatory doses of glucocorticoids typically indicates food hypersensitivity
  • Vomiting
  • Diarrhea
  • Excessive gut sounds, flatulence, and frequent bowel movements
  • Presence of Malassezia dermatitis (fungal skin infections), pyoderma (bacterial skin infections), and otitis externa (outer ear inflammation)
  • Skin plaques: broad, raised flat areas on the skin
  • Pustules: raised skin inflammations containing pus
  • Erythema: skin redness
  • Crusts: dried serum or pus on the surface of ruptured blisters or pustules
  • Scale: flakes or plates of dead skin on the skin’s surface
  • Self-induced baldness due to scratching
  • Skin abrasions/sores caused by scratching
  • Thick, leathery, bark-like skin
  • Hyperpigmentation: darkening of the skin
  • Hives: swollen or inflamed bumps on the skin
  • Giant wheals (elongated marks) on the skin
  • Pyotraumatic dermatitis: skin wound infection due to excessive scratching and bacteria entering the wounds


  • Immune-mediated reactions: These occur when one or more glycoproteins (allergens) are ingested and then presented to the immune system, either before or after digestion. Sensitization can happen as the food moves into the intestine, after absorption of the substance, or both.
  • Non-immune (food intolerance) reactions: These arise from consuming foods with high histamine levels (an antigen known to trigger immune hypersensitivity) or substances that directly induce histamine or through histamine-releasing factors.
  • It is suggested that in juvenile animals, intestinal parasites or infections may damage the intestinal mucosa, leading to abnormal absorption of allergens and subsequent sensitization to certain ingredients.


Your veterinarian will conduct a comprehensive physical examination of your dog, including a dermatological assessment, to rule out non-food-related causes of dermatologic issues. Tests such as a blood chemical profile, complete blood count, urinalysis, and electrolyte panel will be ordered to exclude other potential causes of the disease. Providing a detailed history of your dog’s health, symptom onset, and any relevant incidents, particularly changes in diet or introduction of new foods, is crucial.

For dogs suspected of suffering from adverse food reactions, food elimination diets are recommended. These diets typically consist of one protein and one carbohydrate source that the dog has had limited or no previous exposure to. Improvement may be noticeable within four weeks of starting the new diet, with maximum relief of symptoms observed by thirteen weeks.

If your dog shows improvement on the elimination diet, a challenge is conducted to confirm whether the original diet triggered the adverse reaction. During the challenge, your dog is fed its original diet, and a return of symptoms indicates that something in the diet is causing the reaction. The challenge period should continue until symptoms recur, but not exceeding ten days.

Upon confirming an adverse food reaction, a provocation diet trial is initiated by reintroducing a single ingredient to the elimination diet. Each ingredient is added one at a time, allowing sufficient time to observe any adverse reactions. If no physical response occurs, the next ingredient is introduced. The provocation period for each new ingredient should not exceed ten days, with symptoms typically appearing within 1–2 days. In case of adverse reactions, discontinue the last added ingredient and wait for symptoms to subside before proceeding.

The ingredients for provocation trials should encompass a variety of meats (beef, chicken, fish, pork, and lamb), grains (corn, wheat, soybean, and rice), eggs, and dairy products. The outcomes of these trials will inform the selection of commercial foods that do not contain the problematic substance(s).


Avoid the food substances that triggered the reappearance of clinical signs during the provocation phase of diagnosis. Your veterinarian may prescribe antibiotics or antifungal medications if secondary pyodermas or Malassezia infections are present.

Living and Management

Eliminate treats, chewable toys, vitamins, and other chewable medications (such as heartworm preventives) that may contain ingredients from your dog’s previous diet. It is important to carefully read all ingredient labels. If your dog spends time outdoors, establish a confined area to prevent foraging and hunting, which can disrupt the test diet. Ensure that all family members are informed about the test protocol and assist in maintaining the test diet clean and free of any other food sources. Cooperation is crucial for the successful treatment of this disorder.

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