Why Do Allergies in Dogs Develop?

Possibly one of the most common ailments that we find in the dog world – some dogs just seem to react to everything!  But, if we know how allergies and sensitivities develop, is it something we can tackle?

Let’s take a look and consider some top tips to support your dog’s health.

What is a dog allergy?

An allergy is an unnecessary immune response to an innocuous substance.  True allergies are often fatal.  More often than not we are faced with sensitivities – which are still an immune response.

What is the immune system?

The purpose of the immune system is to defend itself and keep microorganisms like bacteria, viruses, and fungi out of the body and then destroy any if they happen to get in.

It has three lines of defence.

The innate immune system provides the first line of defence; broadly divided into physical/chemical barriers.

The physical barriers include the skin and the lining of the digestive and respiratory tract.  You can think of the body like a sausage; the skin, keeps everything in, but also things out.

Chemical barriers include tears and saliva along with gastric acid.  But also, the microbiome – which is the community of microbes found in the mouth, lungs, gut and on the skin.

We then have the innate immune system – which is for want of a better phrase a row of white blood cells (and other participants) that engulf and destroy invaders.

The third defence is acquired or adaptive immunity – this is the memory bank.  The cells involved in this response help the body remember antigens that it has encountered before – so it can mount a quicker response before the harmful pathogen causes any damage.

The immune system is trained to recognise its own cells as self and leave them to do their jobs.  It is trained to recognise anything that isn’t self and attack it.

When it works, it works brilliantly and, well, us and our dogs survive.

But, it can get a little too enthusiastic and start responding to things it doesn’t really need to.  This is what we see as autoimmunity, but also allergies and sensitivities and there are a number of reasons for this.

Allergies and Sensitivities

First of all, we may be dealing with an immature immune system, and this all starts back in puppyhood.

When we talk about immune responses, we tend to reference Th1 and Th2.  They are both necessary responses, but a Th2 response is more commonly associated with allergy.

During pregnancy, a strong Th2 response is present to reduce the risk of miscarriage.  What this means is that puppies are born with a Th2 dominance.  This then needs to be balanced and the way in which this occurs is through microbial exposure.

This is what we know as immune tolerance – the immune systems develop through exposure to controlled challenge.

The immune system is like a computer; it has software, but it needs data.

The microbial ecosystem in various mucosal sites is important for the development of the immune system.  The young gastrointestinal tract is colonised soon after birth by a variety of commensal bacteria that influence the development of the immune response both in the gut and systemically. The mucosal immune system in the gut must avoid adverse immune responses to dietary antigens and commensals in the new microbial ecosystem while remaining able to mount an effective response to pathogenic organisms.

In an ideal world, our pets will develop a heathy immune system, and they will have sufficient immune tolerance but also eliminate threats when necessary.  But we don’t always live in an ideal world.

So what else can cause issues with immune responses?

Often allergies and sensitivities are associated with poor barrier function; so there may be damaged or broken skin, a poor microbiome, or damage to the integrity of the gut.

Think of it like an army.  If you have a row of soldiers who are standing shoulder to shoulder, you stand a good chance against the enemy.  Once soldiers start falling, opportunities arise for the enemy to get through.

When skin is damaged, antigens spot their opportunity and sneak in through the gaps.  The same occurs in the gut.  Cells sit tightly together, but when cell integrity fails, under digested food particles and pathogens see their opportunity and sneak out into circulation.

The immune system spots these particles – realises they shouldn’t be there, so mounts a response.  Inflammation is a key part of this response.

The issue is when the barrier remains compromised, more particles sneak through and so you end up in a chronic state of inflammation.

Barrier dysfunction can occur for a number of reasons:
Genetic glitches
Microbiome dysbiosis
Long-term use of medication
Environmental exposure

Detoxification Pathways

The more inflammatory compounds you have in the presence of a response, the more anti-inflammatory compounds you will need to counter this response.  There will also be a heightened need for compounds that break down inflammatory molecules like histamine.  Those suffering with allergic disease often have a higher baseline of histamine, and so clearance of this is important too.  What this means is that detoxification pathways need to be running as smoothly as possible.

Detoxification of dietary histamine normally occurs in intestinal epithelial cells via the enzyme diamine oxidase (DAO) as well as histamine-N-methyltransferase (HNMT) in the liver.

What’s interesting is that there are polymorphisms in the genes that code for the DAO enzyme, but certain medications, including over the counter products are seen to inhibit the activity of DAO enzyme too.

They include:

  • Analgesics – morphine, NSAIDs
  • Antiarrhythmics
  • Antibiotics
  • Antifungals
  • Antimalarial
  • Diuretics
  • Motility agents
  • Muscle relaxants
  • Vitamins – ascorbic acid, thiamine

In addition, detoxification pathways in general are nutrient demanding and they also produce a high number of free radicals.  Sufficient levels of key vitamins and minerals like vitamin A, C, E, B1, B2, B3 and iron, along with cysteine are essential.

Does My Pet Need To Detox

Top Tips to Support a Dog with Sensitivities:

1)  Establish and avoid triggers where possible

Elimination Diets For Dogs

2)  Support barrier function – including both skin and gut barrier health.

3)  Support gut health – maintaining gut integrity is key, as is supporting the health of the microbiome.

What can skew microbiome balance?

  • Undigested food – often a result of poor function in the digestive system
  • Overuse of medications/antibiotics
  • Decreased gastric acid (from PPI or antihistamine use)
  • Decreased pancreatic function
  • Motility disorders
  • Anatomical abnormalities
  • Toxin exposure – cleaning products, flea/worm treatments

What Can Help Gut Dysbiosis?

4)      Aid clearance of histamine – B vitamins are important in supporting the clearance of histamine and are found in meat, eggs, fish, and leafy green vegetables.

A Brief Guide to Histamine Intolerance for Dogs

5)      Support anti-inflammatory pathways – inflammation is a necessary response, but like everything, too much can be a bad thing!  To reign the immune response back in, it sends anti-inflammatory messages.  But sometimes, the anti-inflammatory messages get lost in the inflammatory ones.  So we need to make the anti-inflammatory ones a little bigger and louder.  The addition of omega-3 fatty acids to the diet can help regulate inflammatory responses.  Think SMASH – Salmon, Mackerel, Anchovies, Sardines and Herring!

A Guide to Inflammation in Pets

There can also be genetic glitches which contribute to the development of allergies and sensitivities, which is why they can be so complex to tackle.  In addition, whilst we may know of some nutrients that could support our dog’s health, they may struggle to tolerate the foods that contain them. We often become stuck between a rock and a hard place.  If you feel you may be stuck between a rock and a hard place with your dog, please check out our services to see how we can help.

Thanks for reading,

MPN Team ‍

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