Let’s Talk About Skin Barriers, Allergies, and Filaggrin
One of the most important jobs your dog’s skin has is protection.
Actually, it has two big jobs:
- Acting as a physical barrier that keeps moisture in and irritants out
- Acting as an immune barrier, helping defend against allergens, bacteria, and pathogens
Here at Your Canine Nutritionist, skin issues and allergies are something I work with a lot. So let’s take a closer look at one important piece of the puzzle — and why some dogs seem more prone to skin problems than others.
When the skin barrier doesn’t work properly
A weakened skin barrier is a key feature of chronic inflammatory skin conditions like canine atopic dermatitis. One protein that plays a major role in keeping the skin barrier strong is called filaggrin.
In human medicine, mutations in the FLG gene, which codes for filaggrin, are strongly linked to atopic dermatitis and other allergic conditions. While most of this research comes from human studies, we see very similar patterns in dogs with chronic skin disease — suggesting that impaired filaggrin function may also be relevant in our canine companions.
So let’s break this down in a way that actually makes sense.
What exactly is filaggrin?
Filaggrin (short for filament-aggregating protein) is a structural protein found in the outer layers of the skin.
It’s produced from a larger precursor called profilaggrin, which is stored in the upper layers of the epidermis. As skin cells mature, profilaggrin is broken down into filaggrin.
Filaggrin’s job is to:
- Bind keratin fibers together inside skin cells
- Help skin cells flatten and toughen
- Form the cornified cell envelope (CCE) — the outermost protective layer of skin
These flattened cells (called corneocytes) are surrounded by a lipid layer made up of fats like ceramides, cholesterol, and fatty acids. Together, this structure keeps the skin:
- Hydrated
- Flexible
- Waterproof
- Resistant to allergens and irritants
When filaggrin levels are low, this barrier doesn’t form properly. Skin becomes dry, cracked, and more permeable — making it much easier for allergens and irritants to get in.
Why this matters in allergic dogs
In both people and dogs with atopic dermatitis, research shows a strong association between reduced filaggrin function and skin disease.
Dogs with impaired skin barriers are more likely to experience:
- Chronic itch
- Redness and inflammation
- Recurrent bacterial and yeast infections
- Sensitivity to environmental allergens
And here’s an important point:
Filaggrin deficiency doesn’t have to be genetic.
Genetics vs environment (it’s not one or the other)
Some dogs may be genetically predisposed to weaker skin barrier function. However, environmental factors can also reduce filaggrin expression, even in dogs without a genetic mutation.
This means skin issues can be:
- Genetically influenced
- Environmentally triggered
- Or most often — a combination of both
Environmental factors that affect filaggrin
1. Humidity
Low humidity environments can increase the breakdown of filaggrin. Human studies show that people with atopic dermatitis often improve when spending time in more humid climates.
This may help explain why some dogs flare seasonally or worsen during dry winter months.
2. Mechanical damage (scratching)
Scratching, rubbing, and friction damage the skin barrier and trigger inflammation. Unfortunately, inflammation itself can further down-regulate filaggrin, creating a vicious cycle:
- Itch → scratching → inflammation → weaker barrier → more itch
3. Skin irritants (including grooming products)
Certain surfactants — such as sodium lauryl sulfate (SLS) — are known to damage the skin barrier and reduce filaggrin expression.
SLS is commonly used because it creates foam, but it’s also:
- A known skin irritant
- Used experimentally in research to induce barrier damage
You may find it in:
- Shampoos and conditioners
- Detanglers and sprays
- Deodorizing products
- Some medicated or “anti-itch” formulas
This is why ingredient choice in grooming products matters just as much as food.
Inflammation and stress also matter
Inflammation itself suppresses filaggrin production. In animal models, even without environmental triggers, reduced filaggrin function is linked to spontaneous skin inflammation and a lower threshold for allergic responses.
Psychological stress also plays a role. Stress hormones influence immune signaling in the skin, leading to:
- Increased cytokine release
- Heightened itch and inflammation
- Further suppression of barrier repair
This is one reason stress management can be an important — and often overlooked — part of skin health.
What about breed differences?
Some early studies suggested certain breeds (like Labradors and West Highland White Terriers) might be over-represented. However, follow-up studies in different regions haven’t consistently confirmed this.
At this point, there isn’t enough data to definitively link specific breeds to FLG mutations — but genetics likely still plays a role.
Human research also suggests allergy risk can be passed from mother to offspring. While this hasn’t been proven in dogs, it raises important questions about breeding practices and early-life health.
So what does this mean for your dog?
Skin disease is never simple.
It’s influenced by:
- Genetics
- Environment
- Immune function
- Stress
- Topical exposures
- Nutrition
At Your Canine Nutritionist, my approach is always to support the body as a whole — improving skin barrier function from the inside out while also reducing external triggers wherever possible.
That means:
- Supporting barrier repair nutritionally
- Reducing inflammatory inputs
- Being mindful of grooming products
- Addressing stress and gut health
No single product or strategy fixes everything — but thoughtful, layered support can make a meaningful difference.
Final thoughts
Filaggrin plays a vital role in maintaining a healthy skin barrier. When that barrier is compromised — whether due to genetics, environment, or inflammation — dogs become far more vulnerable to chronic skin issues.
Understanding why your dog’s skin is struggling is the first step toward improving it.
If your dog is dealing with ongoing skin or allergy issues and you’d like support navigating diet, supplements, and environmental factors, I’m here to help.
Thanks for reading,
— Martina, Cert. PN
Your Canine Nutritionist