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For pet parents whose dog's skin is itchy and prone to allergic reactions...
welcome to what you need to know about histamine.
Most dog parents know histamine as a part of our dogs' (and our) immune system that triggers itchy skin, dry skin, watery eyes, and serial sneezing.
As humans, we're all pretty used to the idea of taking an ANTI-histamine to alleviate those kinds of itchy skin conditions and allergy symptoms in ourselves.
But what is histamine, how does it work in our dogs' bodies, and which foods, nutrients, and probiotics help break down and balance it?
And what role does histamine play in our dogs' seasonal allergies, food allergies/food sensitivities, environmental allergies, and general allergy symptoms...
What histamine is
Science describes histamine as a water soluble, biogenic amine derived from the amino acid histidine. To translate that into everyday terms: We tend to associate histamine as the thing that makes us sneeze or itch.
While true, histamine is also a neurotransmitter, stimulates gastric secretion, and is a vasodilator. It also plays a role in sexual reproduction. Histamine is critical for immune function through inflammatory response (when histamine in action is easily observed by pet parents) and is released by mast cells.
Keeping histamine in balance is important overall to your pet's health, to your pet's healthy skin, and maintaining your dog's coat health, while avoiding skin and coat issues.
Here's what you need to know about histamine, your dog's skin and coat, and how to treat skin disorders to help your dog stop itching!
3 keys to histamine all dog owners of itchy dogs should know...
(from a canine nutritionist/dog mom perspective)
Key tip 1: Visualize the histamine "bucket"... and how it can help prevent allergy symptoms and support healthy skin & coat
Too much of many things, even when important, can be a negative. You may remember I’ve talked about visualizing a histamine bucket before. When this bucket overflows with histamine (beyond what the body can handle), disturbances to your dog's skin health, coat, and stool happen. So that, of course, means we always want to keep our dogs' histamine levels well below what their bucket can comfortably handle.
What does that actually mean?
Dogs make histamine in their bodies and histamine can also come from food sources. Disturbances to hormones can also affect the body’s ability to break down histamine and add to the overall histamine load.
Fortunately, the body has ways to break down histamine. DAO, one of the digestive enzymes, breaks down histamine, reducing its level in your dog's "bucket." Certain hormones can increase or decrease the rate at which enzymes work to break down and reduce histamine. Estrogen, for example, can down-regulate DAO - making it less effective in lowering histamine levels.*
It's not always just your dog's skin - histamine overload can look like GI issues/ food allergies too...
When it comes to histamine and dogs, most of us are concerned about managing skin issues like irritated skin and skin allergies. However, sometimes a histamine issue also manifests with GI disturbances and can be confused with a food allergy.
Pro tip: make sure any gut health problems are cleared to make histamine elimination possible
Keep in mind that as the body breaks down compounds it also has to excrete them. Before reaching for herbs or nutritional supplements that help the body break down histamine, make sure the pathway out is clear. In other words, gut condition must be addressed. Fortunately, these often go hand in hand -- especially because histamine can certainly affect the gut.
Key tip 2: Which nutrients & foods in your dog's diet are recommended for dogs with itchy skin?
Nutrients in your dog's food or supplements to help lessen histamine load & prevent allergy symptoms:
- Copper- Copper is essential for the breakdown of histamine. Generally speaking, diets that contain liver from ruminant animals (ex: cows) will be rich in copper.
Pro tip: Beware of over-supplementing zinc which can harm copper effectiveness by stimulating a protein in the gut to bind up the extra zinc. This protein has a higher affinity to copper so makes copper less available. Many dog owners with an itchy dog innocently supplement zinc without being aware of the dose or ensuring optimal levels of copper. (Not to mention, zinc may not be needed in the first place.)
Typically, copper from turkey, chicken, and pork liver is either unavailable or at levels too low to meet the dog’s requirements.
- B6 - an enzyme needed to break down histamine. If your pet's food is cooked and low in B6 combined with an increased histamine load in the food (see below), it can lessen your dog’s ability to break down histamine.
- Vitamin C - is also used with B6 and copper to clear histamine. Dogs can synthesize vitamin C from glucose. However, dogs are not as equipped to do this relative to other animals. They can rev up production when they need it, but not necessarily at optimal rates.
- Vitamin E - helps the modulation of release of histamine in the body. Vitamin C is needed to regenerate E -- so its purpose is multifold. I recommend supplementing vitamin E in d-alpha tocopherol form with mixed tocopherols.
- Vitamin A & D: Ultimately, we could keep going down the rabbit hole because nutrients all work together. When it comes to immune function, though, vitamin A & D work together to help modulate histamine release and prevent chronic inflammatory conditions and reduce inflammation resulting from deficiency. Beef liver provides plenty of A, but can fall short on vitamin D!
Recommended food - for dogs with itchy skin and other allergic-reaction issues:
- Kidney: is potentially quite rich in DAO. I often include it in diets where I am working with histamine-related issues. Kidney is also rich in selenium, important for the antioxidant defense system and directly affects histamine levels and lowering levels.
If hormone issues are suspected, an entire other list of foods would be important.
Key tip 3: Higher histamine foods to be aware of - for dog owners of dogs prone to allergic reactions
Foods rich in histamine to limit/avoid:
- Aged foods- including dairy products (like aged cheese) and meat products
- Canned foods- especially fish. Canned sardines are very high histamine (Canned foods are higher in histamines, and sardines are also high, so canned sardines is a bit of a double whammy - even though sardines is excellent for other reasons in your pup's food.)
- Food stored for any length of time in the fridge - Histamine levels rise when food is left in the fridge (cooked food). Better to freeze until you're ready to use.
And... bananas and pineapples are thought to be histamine liberators. Pork may also fall into this category. Which means that while not being high in histamines themselves, they do "liberate" histamine, causing more to be released.
Final tips for parents of dogs who are constantly scratching, dealing with severe allergies, & skin problems (dry skin, itchy skin, sensitive skin, dull coat)
Raw diets are not essential, but they can be useful because they do not contain the histamine load that cooked foods can have when sitting in the fridge.
Some probiotics are useful for aiding in histamine breakdown -- but some can make histamine even worse. Each probiotic strain should be assessed as to whether they are neutral, beneficial, or contraindicated. (An area where a certified nutritionist consult could be helpful.)
Some drugs may reduce the presence of DAO in the gut and could potentially make some dogs more sensitive to histamine intake.
Some have mistakenly suggested reducing histidine in the diet. Please don’t do this as it does not solve the issue at hand.
For most dogs, when I suspect histamine-related issues, I go beyond the recommended allowance for zinc, copper, and selenium. Please don’t supplement these without using nutrient requirements and/or consulting with a professional nutritionist as each one is unsafe at excessive levels. Copper comes from high quality sources- preferably liver- as liver will also contribute vitamin A.
I often use cruciferous veggies. I avoid foods high in histamine such as canned fish and I skip the fermented food. Depending on the presence of MCT or hormonal disturbances, additional therapies may be needed. Herbs can also be useful- but first make sure we have addressed the nutrients (essential and non-essential) and addressed the gut.
While all diets should use nutrient guidelines, some nutrients are considered non-essential (Vitamin C) and need to be independently dosed. Some nutrients are beneficial when raised above the recommended allowances, as described.
If you have any questions on histamine and your dog's diet, let me know!
*Note on the intersection of estrogen, histamine, & other conditions: Estrogen and progesterone also have a role in mast cell tumors (MCT - another topic for another day). More studies are required, but in studies not relating to dogs, estrogen clearly reduces the activity of one of the important digestive enzymes, DAO. I personally see dogs where we are working with MCT-related issues and itchiness -- coupled with hormonal issues. Veterinary advice is essential in these cases, so it's important that a veterinarian is part of the pet care team here. Diet still plays a critical role where ingredients and nutrients can be controlled to help support the dog's histamine release, load, and breakdown.*
Small Animal Clinical Nutrition
Canine and Feline Nutrition
NRC Nutrient Requirements of Dogs and Cats
Canine and Feline Gastroenterology