The difference between hypoallergenic and anallergenic pet foods is subtle but important. The Greek prefix hypo- 鈥渓acking鈥� or 鈥渓ess.鈥� Hence, someone who is hypothermic is lacking in heat, and someone who is hypoglycemic has less blood glucose than they should. The prefix a- (or an- when it proceeds a word that starts with a vowel) is also Greek but 鈥渘o,鈥� 鈥渘ot,鈥� or 鈥渁bsence of.鈥� We see this in terms like apolitical (not political) or anorexia (absence of appetite). Thus, hypoallergenic dog food contains fewer allergens, whereas anallergenic dog food contains none (or as close to none as possible).
What does that actually mean for pet food? Well, for most cats and dogs, proteins are the primary allergen, so tend to use partially hydrolyzed proteins or proteins that have been broken down into smaller pieces and are therefore less likely to be recognized by an animal鈥檚 immune system, triggering a reaction. They tend to use a single source of protein instead of a blend and a single source of carbohydrates. Hypoallergenic pet foods often avoid the most common allergens for cats or dogs, sometimes employing specific parts of these animals鈥攈ydrolyzed chicken liver is common鈥攐r novel and 鈥渨eird鈥� protein sources like kangaroo, rabbit, or soybeans.
The problem is that roughly will still have allergic reactions when fed hydrolyzed diets derived from proteins they鈥檙e allergic to. This may be due to incomplete hydrolyzation, leaving protein fragments still big enough to be recognized by the immune system, or even just cross-contamination from some part of the manufacturing process. For dogs like this, veterinarians often turn to anallergenic diets.
Proteins are long chains of amino acids. Their mass is measured in a unit called a Dalton (Da), or more commonly, a kilo-Dalton (kDa) because scientists prefer working with smaller numbers whenever possible. Protein masses can vary widely. For example, insulin has a mass of roughly , whereas ATP synthase, the enzyme responsible for powering everything we do, has a mass close to . Alcohol dehydrogenase, the enzyme that processes any alcohol we drink, weighs roughly .
There isn鈥檛 a consensus on how big a protein needs to be to potentially trigger an immune response, but we can confidently say that the smaller the protein, the lesser the chance. Hypoallergenic dog food tends to have proteins in the range. Conversely, 鈥攄ebuted in 2012 after over a decade of research鈥攚as the first pet food considered to contain extensively hydrolyzed proteins. It contains proteins that are less than 1 kDa and broken down to the level of single amino acids!
In one randomized, double-blind crossover of 10 dogs with cutaneous adverse food reactions, the Royal Canina Anallergenic diet did not trigger an allergy flare-up in a single participant. In contrast, a hydrolyzed chicken liver diet (a typical protein source for hypoallergenic dog foods) triggered a flare-up in 40%.
Despite being a feat of scientific engineering designed to help dogs and cats get relief from a condition without many other treatments, there remains a degree of controversy around Royal Canin鈥檚 Anallergenic food. Why? Because its protein source is hydrolyzed poultry feathers.
Pet food marketing has long relied on messages about feeding your dog as you would the other members of your family or avoiding 鈥渇iller鈥� ingredients. Unfortunately, this has resulted in demonizing ingredients like corn meal or hydrolyzed poultry feathers, even when all science supports their inclusion. Despite infused commercials referring to domestic dogs as 鈥渨olves鈥� or 鈥渃arnivores,鈥� your Shih Tzu has evolved quite a bit from her wolf days and has different dietary requirements.
Dogs are not carnivores and haven鈥檛 been for thousands of years. They can digest grains quite well and benefit significantly from modern advancements in food processing, just like humans. Raw diets are dangerous for a multitude of reasons, and just because you wouldn鈥檛 want to eat an ingredient like hydrolyzed poultry feathers doesn鈥檛 mean it isn鈥檛 perfectly beneficial to your pet. Not to mention, as the poultry feathers are so extensively broken down before being included in kibble, it makes about as much sense to consider them feathers as you鈥檇 consider a single brick a cathedral.
All of the dogs in the above-mentioned crossover study readily ate the feather-based food, and such diets even for the more traditionally discerning cats. Despite claims to the contrary, hydrolyzed poultry feathers are by both cats and dogs.
Other attempts to demonize poultry feathers as a source of protein rely on characterizing them as a 鈥渨aste product鈥� of human meat processing鈥攁s if that鈥檚 a bad thing. For sustainability purposes, utilizing every part of an animal is far preferable to disposing of a perfectly functional ingredient. Claims that Royal Canin is only using feathers to are equally nonsensical, given how the extensive hydrolyzation process is, the extensive research and development funding that went into perfecting it, and how much cheaper it would be to continue to use the conventional protein sources they already have.
Anallergenic food is a powerful tool for veterinarians and pet owners to severe pet allergies that, prior to its invention, often had no great treatments. The demonization of by-products, highly processed ingredients, or whatever else you want to call hydrolyzed poultry feathers is unscientific rubbish that will almost certainly lead to pets who would benefit from this food not getting it. It鈥檚 high time we overcame our fear of the unknown and instead marvelled at how science can find unique new solutions to age-old problems.
