What is the difference between food allergies and food intolerances (adverse food reactions) in dogs?
Traditionally, the terms food allergy and food intolerance have been used to describe all adverse food reactions in dogs. Food intolerance is the most accurate term for adverse food reactions in dogs. Food intolerance covers a large number of adverse food reactions that do not involve the immune system, and generally cause digestive issues.
The term food allergy or food sensitivity is most accurately applied when the immune system reacts to an allergen (a component of the food that creates signs and symptoms). The allergen is a protein or multiple proteins, and immune system reactions to these proteins generally require several exposures before signs are evident.
Food intolerance in dogs often looks like food allergies, because there are only so many ways that the body can demonstrate a problem with food. One characteristic of food intolerance is that it occurs on the initial exposure to that food or food additive. The incidence of food intolerance versus food allergy is not known.
What kinds of adverse food reactions happen in dogs?
There are several categories of food reactions that may occur in dogs:
1. Food poisoning. Food poisoning is an adverse reaction caused by the direct action of a food on the dog. Food poisoning is a frequent cause of gastrointestinal (GI) disease in dogs, and may occur due to any of the following causes:
- Ingesting excessive amounts of a specific nutrient like vitamin A or vitamin D
- Scavenging spoiled food
- Ingesting specific problematic foods, such as chocolate or dairy products
- Ingesting plants that can cause gastrointestinal irritation, such as aloe vera or daffodils
2. Reactions to food additives. Adverse reactions to food additives are frequently reported in people, including reactions to compounds like sulfites, monosodium glutamate, and spices. Despite an impression that food additives can cause problems in dogs, evidence to support this suggestion is lacking. However, disulfide is one food additive that can cause problems. Disulfides are found in onions and can cause damage to red blood cells.
3. Reactions to certain carbohydrates. There are several important carbohydrate intolerance disorders in humans. Recognized carbohydrate intolerance in dogs is much less frequent. One common carbohydrate reaction in dogs is lactose intolerance. The signs include diarrhea, bloating, and abdominal discomfort after ingesting cow's or goat's milk.
4. Dietary indiscretion. Dogs are famous for eating things they should not. Overconsumption, ingesting items that are not edible, and ingesting garbage are frequent causes of adverse dietary reactions. Gastrointestinal signs may result from bacterial contamination, fat or grease, bones, wood, plastic, or aluminum foil.
How do I know if my dog has a food allergy or food intolerance?
The best way to determine whether your dog is experiencing a food allergy/sensitivity or intolerance is to start by providing your veterinarian with a detailed diet history, including everything your dog currently eats, has eaten in the past, or may have access to. This information can help identify potential triggers for your dog’s symptoms. Your veterinarian may then recommend an elimination diet and food challenge to confirm or rule out specific allergens.
It’s important to distinguish between an adverse food reaction and an immune-mediated food allergy or sensitivity, as the latter often results in recurring skin or gastrointestinal signs that require a more comprehensive management approach. Keeping track of your dog's feeding schedule, nutrient profile, and the timing and severity of any symptoms will help your veterinarian make a clearer diagnosis and guide the most effective treatment plan.
