Itchy dogs? How nutrition and treats with natural protein from fermentation can naturally alleviate allergies.

In a nutshell: Itching in dogs is often discussed as a problem of protein quantity. However, recent research on the gut-skin axis shows: It's not the quantity that's the decisive factor, but the digestibility of the protein. Undigested protein fragments in the gut can trigger an immune response, manifesting as itching, red skin, and increased paw licking. In this guide, you'll learn how to properly evaluate protein sources and what 4 steps you can implement immediately.

If your dog scratches, licks its paws, or develops red skin patches, many owners intuitively diagnose "too much protein in the food." This is one of the most persistent theories in online forums — and at the same time, one of the most inaccurate. In this article, we explain why the digestibility of a protein source is often more important than its quantity, how the gut and skin are biologically connected, and what concrete steps you can take.

When is itching in dogs more than just scratching?

Occasional scratching is normal in dogs. It becomes problematic when the following signs occur together:

• Persistent scratching or gnawing, especially on paws, flanks, or ears
• Redness or flaky skin on the belly, armpits, or between the toes
• Hair loss in typical areas
• Frequent paw licking — until the paws are wet or discolored
• Restless sleep patterns, frequent waking at night
• Changes in stool consistency (softer, slimy, or significantly harder)
• Odor from ears or mouth

If several of these symptoms occur together, it is often not a simple skin irritation — but a systemic problem, which often originates in the gut.

Overview of the most common causes of itching

Before we delve into the protein factor, here are the most important triggers that a vet should investigate:

1. Parasites (fleas, mites, ticks)
2. Contact allergies (cleaning products, carpets, pollen)
3. Atopic dermatitis (genetic predisposition)
4. Food intolerance or allergy
5. Dry skin due to heating or improper care
6. Hormonal diseases (thyroid, Cushing's)
7. Secondary infections with bacteria or yeasts
8. Disrupted gut flora — often overlooked, but now well-documented

The last two points are closely related — and this is precisely where protein quality comes into play.

The underestimated factor: Protein quality and digestibility

The gut-skin axis: Why the gut controls the skin

Around 70% of your dog's immune system is located in the gut. If the gut barrier becomes permeable — technically known as "Leaky Gut" — undigested food fragments can enter the bloodstream. The immune system recognizes these fragments as foreign and initiates an inflammatory response. One of the most visible signs of this reaction: itching and skin inflammation.

A central driver of this cascade is poorly digestible protein. If protein remains undigested in the large intestine, it serves as a substrate for putrefactive bacteria. The resulting metabolic products (ammonia, amines, indoles) irritate the intestinal wall and increase its permeability.

Not all proteins are equal: The digestibility comparison

The so-called true ileal digestibility measures how much of a protein source is actually absorbed in the small intestine — before it reaches the large intestine. The higher this value, the less undigested protein enters the critical zone.

Source: MicroHarvest digestibility data (INFOGEST method, 2024). Comparative values from Oba et al. 2023, Journal of Animal Science.

A glance at the table shows: There is a difference of over 20 percentage points between the most digestible and the least digestible protein. For daily feeding, this concretely means: A dog receiving 40 g of protein per day via potato protein will have approximately 11 g undigested protein passing into the large intestine. With fermentation protein, it's only about 1.5 g. This is the biological difference between "gut at rest" and "gut constantly irritated."

What does "high-quality protein" mean scientifically?

The quality of a protein source is determined by three factors:

1. Amino acid profile — does the protein contain all essential amino acids in sufficient quantities?
2. Digestibility — how much of it can the body actually absorb?
3. Freedom from irritants — no heat damage, no anti-nutritional factors, no contaminants

The DIAAS value (Digestible Indispensable Amino Acid Score) developed by the FAO combines these factors. Values above 100% are considered "high-quality" — the protein can be the sole protein source. According to peer-reviewed research, fermentation protein achieves DIAAS values above 100% for adult dogs — on par with chicken meat, with significantly higher digestibility (Oba et al. 2023, Journal of Animal Science).

4-step plan: What you can do specifically for itching

Step 1: Ensure veterinary clarification

Before you change the food: Have parasites, skin diseases, and hormonal causes ruled out. A skin swab and a blood test cost little and prevent you from searching in the wrong place for months.

Step 2: Conduct a feed audit

Carefully examine the ingredient list of your current dog food:

• What is the first declared protein source?
• Is it declared as food-grade quality or as "animal by-products"?
• Are there any artificial preservatives (BHA, BHT, propyl gallate)?
• What is the proportion of filler ingredients (corn, wheat, rice flour without nutritional value)?

You can often recognize poor protein sources by vague declarations: "Meat and Animal Derivatives" leaves room for everything — from muscle meat to feathers and cartilage. This makes digestibility unpredictable.

Step 3: Change protein source — and do it specifically

Instead of simply feeding "less protein," switch to a highly digestible, hypoallergenic alternative. Fermentation protein meets both criteria: high digestibility (95–97%) and hypoallergenic properties, because it contains no classic allergens like chicken, beef, or milk protein. A recent study with 30 dogs (de Matos & Cruz 2025) also showed: 72% of dogs preferred food with 10% fermentation protein over a conventional fish-and-rice recipe. 91% of owners reported equal or even higher food intake during the transition.

Practical for you: The Besserli Trial Pack contains both our chicken and vegan variants with fermentation protein — ideal for checking which variety your dog accepts better.

Step 4: Support gut health

In parallel with the protein change, targeted gut strengthening can be beneficial:

• Probiotics (e.g., Enterococcus faecium) — as a course for 4 to 6 weeks
• Prebiotics (e.g., chicory, inulin) — as a nutritional base for good bacteria
• Omega-3 fatty acids (salmon oil, flaxseed oil) — anti-inflammatory
• Timeframe: Give the gut at least 6 weeks. Visible skin improvements often only appear after 4–8 weeks

You can find a complete plan for this in our guide to gut rehabilitation for dogs.

Why fermentation protein is a structurally different solution

Traditional animal proteins are heated at high temperatures — this can damage so-called reactive lysine (the bioavailable part). In chicken meal, the ratio of reactive to total lysine is only 0.86 — an indication of heat damage. Fermentation protein shows values above 0.9 here — almost no heat damage (Oba et al. 2023).

Further structural advantages:

• Hypoallergenic — no cross-reactions with classic food allergens
• No anti-nutritional factors — unlike soy or some legumes
• Consistent amino acid profile — due to standardized fermentation in bioreactors, not dependent on batch, slaughter year, or origin
• Non-GMO, minimally processed, free from contaminants

When you should definitely see a vet

Seek veterinary help if:

• The itching persists for longer than 2 weeks despite a change in diet
• Bloody spots, scabs, or open skin lesions appear
• Your dog becomes apathetic or has a fever
• Diarrhea, vomiting, or weight loss occur simultaneously
• You cannot rule out hormonal causes (thyroid, Cushing's)

A dietary improvement never replaces a veterinary diagnosis — it complements it.

Frequently Asked Questions

Can too much protein in dogs cause itching?
The sheer quantity is rarely the problem. What matters is how well the protein is digested. Hard-to-digest protein leaves undigested fragments in the gut, which can irritate the immune system — this can manifest as itching.

Which protein source is best for itching?
An ideal choice is a highly digestible, hypoallergenic protein source. Fermentation protein achieves 95–97% digestibility and contains no classic allergens. Hydrolyzed proteins, insect protein, or rarely used animal proteins (horse, kangaroo) can also help.

How long does it take for the skin to calm down after a diet change?
Initial improvements often appear after 2–3 weeks, with significant skin improvement typically seen after 4–8 weeks. Give your dog at least 6 weeks before making a judgment.

Are probiotics really useful for dog itching?
Yes — if the itching is related to a disturbed gut flora. Probiotics alone are rarely sufficient; they work best in combination with a highly digestible protein source and prebiotics.

Is fermentation protein safe for dogs?
Yes. The protein is GMP+ certified, regulatory approved for FEDIAF markets, and has been tested in palatability and digestibility studies with dogs. It is hypoallergenic and free from contaminants.

Can I switch the food overnight?
Better not. Gradually mix in the new food over 7–10 days: Days 1–3 = 25% new, Days 4–6 = 50%, Days 7–9 = 75%, from Day 10 = 100%. This helps avoid additional digestive irritation.

Which Besserli variant is suitable for itching?
Besserli Vegan is the most hypoallergenic variant — without classic animal proteins, only with fermentation protein and natural plant-based ingredients. For dogs without protein allergies, Besserli Chicken is also suitable.