The environment and lifestyle of our pets seem to have a relationship to environmental allergies. Pets living, or exposed to, an urban lifestyle are exposed to microbes from natural environments creating a protective effect against the development of allergies. Whereas those living in a rural environment have a reduced amount of natural microbes and an increase in the microbes found in human microbiomes, increasing the prevalence, and severity, of allergies. Single-dog homes seem to also show an increase in allergies compared to multi-dog households.

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Environmental allergies are a common dermatological disease affecting both dogs and cats. Although the manner in which the disease develops is not understood, there is evidence that genetic abnormalities, a weakened immune system, and a skin barrier dysfunction are associated with inflammatory responses when allergen triggers are present. Environmental allergies are also referred to as canine atopic dermatitis (CAD) in dogs, affecting around 10-15% of the population, and feline atopic-like dermatitis in cats. It is well documented that CAD is often associated the production of IgE against environmental allergens, but the function of IgE in cats is not entirely clear.

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Just like the gut contains a large diversity of microbiota, the skin has its own microbiome and cells that work together to form the skin, the largest habitat of both “good” and “bad” microorganisms. A disruption to the cells or the microorganisms can create an imbalance and affect our pets. Our pet’s skin microbiome is inhabited by microorganisms that are beneficial to them. They act like little soldiers fighting pathogenic microbes in a constant battle for nutrients, metabolites, and modulating their immune system. This microbiome includes a large range of bacteria, archeae, fungi, viruses, and parasites. The skin microbiome is not limited to the surface and is present in the deep dermis and subcutaneous tissues.

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A skin barrier dysfunction affects the permeability of the skin thus affecting how it deals with external threats and is believed to be a secondary consequence of atopic dermatitis, known as the inside-outside hypothesis. It is believed that this weakened state of the skin leads to an increase in the penetration of allergens. Upon contact with an allergen the inflammatory response triggers the release of cytokines and IgE antibodies. Cytokines are responsible for communication between cells and are both pro-inflammatory and anti-inflammatory. In simplest words, they signal the body on how to react. Immunoglobulin E (IgE) is responsible for the immunity against parasites. The type and amount of these cells triggered will determine the severity of the allergic response. This weakened state of the skin also leads to a breakdown in the proteins of the skin affecting natural moisturizing factors such as free amino acids and small peptide concentrations, affecting the capacity of the skin to retain water.

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So what does all that mean?

• The hydration of the skin is affected, leading to dry skin

• It creates skin inflammation

• It can create skin lesions

• It can allow for secondary bacterial infections

The most common environmental allergens are dust, dust mites, pollen, mold, plants, soap and detergents, and even hard water.

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Clinical Signs

The most common signs in dogs include redness of the skin, severe itching and inflammation that can result in alopecia, repetitive and compulsive picking at the skin, and secondary infections with papules, pustules and crust. The most common locations where they develop are axillae, distal extremities, inner ear, around the eyes and outer ear. Dogs can have non-cutaneous signs manifested in the gut and respiratory system but is predominantly presented on the skin.

In cats, the most common cutaneous signs are head and neck severe itching and inflammation, miliary dermatitis, self-induced alopecia, eosinophilic granulomas, and eosinophilic plaques. Additional non-cutaneous signs are sneezing, coughing, conjunctivitis, diarrhea, or vomiting.

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Natural Dietary Supplements

• Essential fatty acids (EPA and DHA) – can help improve the coat quality, strengthen the skin barrier and reduce water loss of the skin

• Probiotics – they help strengthen the immune system and down regulate the hypersensitivity response to allergens. Lactobacillus species have shown reduction in inflammatory responses

• Quercertin – Also known as “Nature’s Benadryl” contains antihistamine properties to aid the allergic response

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*Allergen immunotherapy should only be discussed with a vet. We will NOT advise on the use of medications, including, but not limited to over-the-counter antihistamines*

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It is impossible to distinguish between food induced atopic dermatitis and environmental atopic dermatitis but there are ways to help determine which could be the cause. Allergic reactions that occur during a season of the year, after exposure to an environmental trigger affects the paws first, or any site on the body that the animal is able to scratch, around the nose is an indication that the reaction is environmental and not food related. Atopic dermatitis is diagnosed by history, clinical examination and exclusion of differential diagnosis. False positives are commonly seen in intradermal and serum IgE tests but are still useful and safe as diagnostic tools, only, if used in conjunction with the pet’s history.

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References Skin microbiota and allergic symptoms associate with exposure to environmental microbes By Jenni Lehtimäki, Hanna Sinkko, Anna Hielm-Björkman, Elina Salmela, Katriina Tiira, Tiina Laatikainen, Sanna Mäkeläinen, Maria Kaukonen, Liisa Uusitalo, Ilkka Hanski, Hannes Lohi, Lasse Ruokolainen Year: 2018 Container: Proceedings of the National Academy of Sciences Volume:115 Issue:19 Page:4897-4902 DOI:10.1073/pnas.1719785115 New perspectives on epidermal barrier dysfunction in atopic dermatitis: Gene–environment interactions By Michael J. Cork, Darren A. Robinson, Yiannis Vasilopoulos, Adam Ferguson, Manar Moustafa, Alice MacGowan, Gordon W. Duff, Simon J. Ward, Rachid Tazi-Ahnini Year: 2006 Container: Journal of Allergy and Clinical Immunology Volume:118 Issue:1 Page:3-21 DOI:10.1016/j.jaci.2006.04.042 Longitudinal Evaluation of the Skin Microbiome and Association with Microenvironment and Treatment in Canine Atopic Dermatitis By Charles W. Bradley, Daniel O. Morris, Shelley C. Rankin, Christine L. Cain, Ana M. Misic, Timothy Houser, Elizabeth A. Mauldin, Elizabeth A. Grice Year: 2016 Container: Journal of Investigative Dermatology Volume: 136 Issue:6 Page:1182-1190 DOI:10.1016/j.jid.2016.01.023 The canine and feline skin microbiome in health and disease By J. Scott Weese Year: 2013Container: Veterinary Dermatology Volume: 24 Issue: 1 Page:137-e31 DOI: 10.1111/j.1365-3164.2012.01076.x The feline skin microbiota: The bacteria inhabiting the skin of healthy and allergic cats By Caitlin E. Older, Alison Diesel, Adam P. Patterson, Courtney Meason-Smith, Timothy J. Johnson, Joanne Mansell, Jan S. Suchodolski, Aline Rodrigues Hoffmann Year:2017 Container: PLOS ONE Volume: 12 Issue: 6 Page:e0178555 DOI:10.1371/journal.pone.0178555 The cutaneous ecosystem: the roles of the skin microbiome in health and its association with inflammatory skin conditions in humans and animals By Aline Rodrigues HoffmannYear: 2017 Container: Veterinary Dermatology Volume: 28 Issue:1 Page: 60-e15 DOI:10.1111/vde.12408