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The "invisible" allergy affecting millions of cats

Your cat:

  • It **scratches** persistently.
  • Has **inflamed skin**.
  • **Vomits** repeatedly.
  • Has recurring **diarrhea**.
  • Coat is **damaged**.

You’ve tried various foods with no improvement. Perhaps you’re dealing with **feline food allergy**: one of the most underestimated conditions.

And the 5 most "culprit" ingredients might surprise you.

Food allergy in cats

What it is: adverse immune reaction to one or more components of food.

Difference with intolerance:

  • Allergy: involves the immune system.
  • Intolerance: non-immune digestive issue.

Frequency:

  • 10-15% of dermatitis in cats.
  • Often associated with gastrointestinal issues.

Typical symptoms

Skin

Most frequent:

  • Intense itching (head, neck, abdomen).
  • Compulsive licking (overgrooming).
  • Crusts and redness.
  • Hair loss (alopecia).
  • Self-trauma (scratches, wounds).

Gastrointestinal

Common:

  • Repeated **vomiting**.
  • **Chronic diarrhea**.
  • **Flatulence**.
  • **Borborygmi** (intestinal noises).
  • **Weight loss** (long-term).

Others

  • Recurring **otitis**.
  • Allergic **conjunctivitis**.
  • Feline **asthma** (rare).

The 5 most allergenic ingredients (it will surprise you)

1. Chicken (surprising!)

The **number one culprit** of feline allergies.

Yet it is the **most common ingredient** in commercial foods. Why?

Continuous chronic exposure → sensitization.

Solution:

  • Food with **alternative proteins**.
  • Rabbit, duck, venison, lamb.

2. Fish

Second most frequent.

Surprising because:

  • Often considered "hypoallergenic".
  • In reality, a frequent cause of allergies in cats.

"Fish-rich" food common in commercial products = high exposure.

3. Beef

Less frequent in cats compared to dogs.

4. Dairy

Many adult cats are **lactose intolerant** (loss of lactase after weaning).

Milk, yogurt, cheeses = digestive issues.

Exceptions: some cats tolerate fermented yogurt (lactose digested).

5. Grains (corn, wheat, soy)

Frequent in cheap foods.

High carbohydrates + plant proteins = problems.

Symptoms are not what you expect

Common mistake: thinking that allergy = immediate symptoms after a meal.

Truth:

  • Symptoms can appear **after hours or days**.
  • Often **chronic and fluctuating**.
  • Not related to individual meals.

It’s difficult to identify without the correct diagnosis.

Diagnosis: the elimination diet

The only way to diagnose food allergy in cats.

What it is

Feed the cat **only** with:

  • **One "novel" protein** (never eaten before).
  • **One "novel" carbohydrate**.

For **8-12 weeks**.

"Novel" proteins

  • Rabbit.
  • Duck.
  • Venison.
  • Horse.
  • Kangaroo (in some specific foods).
  • Insects (in recent commercial foods).

Never used before by the cat.

"Novel" carbohydrates

  • Potato.
  • Tapioca.
  • Pea (with caution: some consider proteins).

The options

Hypoallergenic commercial food:

  • Royal Canin Hypoallergenic.
  • Hill's z/d.
  • Purina HA.

Hydrolyzed proteins:

  • Proteins "broken" into pieces too small to be recognized by the immune system.

Homemade food:

  • Only with certified veterinary nutritionist advice.

The strict rules

During the diet:

  • ❌ **No varied snacks**.
  • ❌ **No human food**.
  • ❌ **No treats** not part of the diet.
  • ❌ **No flavored vitamins** (some contain flavors).
  • ❌ **No food for other animals** in the house (the cat may steal).

Even **a small "violation"** = start over.

The expected results

After 8-12 weeks:

If it is a food allergy:

  • Symptoms improve by 50-80%.
  • Better skin and coat.
  • Calm gastrointestinal tract.

If no improvement:

  • Probably not a food allergy.
  • Investigate other causes (environmental allergies, etc.).

The final "challenge"

Once improved, **reintroduce** suspected ingredients:

  1. Chicken for 1-2 weeks.
  2. If symptoms return: chicken allergy confirmed.

This way you identify the specific allergen.

Blood tests

IgE specific for food allergies:

  • Available but **poorly reliable** for cats.
  • Many false positives and negatives.
  • **DO NOT replace** the elimination diet.

Conclusion: the elimination diet remains the **gold standard**.

Long-term management

Once the allergen is identified:

Option 1: specific commercial food

  • Royal Canin Hypoallergenic.
  • Hill's z/d.
  • Purina HA.

For life.

Cost: 80-130 €/month.

Option 2: "limited ingredient" food

Food with one type of "rare" protein (rabbit, duck).

Premium brands:

  • Almo Nature.
  • Schesir Hairball.
  • Wild Freedom Adult.

More economical (60-100 €/month).

Option 3: rotation

For less reactive cats:

  • Rotation of different proteins.
  • Rabbit → duck → venison.

Avoids chronic sensitization.

Option 4: homemade food

Only with certified nutritionist advice.

Customized recipe.

Signs of "non-food" allergies

Environmental allergy (atopy):

  • Pollen, dust mites, molds.
  • Often seasonal.
  • Response to antihistamines.
  • **Does not improve** with elimination diet.

Flea allergy (FAD):

  • Even one flea triggers.
  • Hair loss at the base of the tail.
  • Resolves with antiparasitics.

Specific foods for allergic cats

Top options:

  1. Royal Canin Hypoallergenic:
    • Hydrolyzed proteins.
    • Veterinary reference.
    • Cost: 18-25 € for 2 kg.
  2. Hill's z/d:
    • Hydrolyzed.
    • Traditional and reliable.
  3. Purina Pro Plan HA:
    • Proteins reduced to small peptides.
  4. Hypoallergenic single protein foods:
    • Almo Nature only rabbit.
    • Catz Finefood Single Protein.
  5. Balanced homemade food:
    • With nutritionist.
    • Cost: variable.

The complications of untreated allergies

  • **Chronic skin lesions** (with possible infections).
  • **Chronic gastrointestinal symptoms**.
  • **Reduced quality of life**.
  • **Chronic stress** for the cat.
  • **Recurring veterinary costs** for symptomatic therapy.

The frequent story

Typical case:

Cat with itching, licking, recurring vomiting.

Attempts:

  • Generic "premium" food: nothing.
  • "Natural" food: nothing.
  • "Grain free" food: nothing.
  • Antihistamines: nothing.
  • Cortisone: temporarily improves.

Final diagnosis: allergy to **chicken** (ingredient in all tried foods).

Solution: food based on **rabbit**.

Result: cat recovered.

Time lost: often years of symptoms.

The truth

Food allergy in cats is:

  • **More common** than one might think.
  • **More insidious** than one might think.
  • **Treatable** with the correct diagnosis.

Key:

  1. Suspicion in unresolved chronic cases.
  2. Elimination diet 8-12 weeks.
  3. Allergen identification.
  4. Specific food for life.

Initial investment: time (3 months for diagnosis).

Benefit: cat healed.

And the 5 "culprit" ingredients — chicken, fish, beef, dairy, grains — are often the **most common** in commercial foods. Ironic, isn’t it?

If your cat has unexplained chronic symptoms, consider food allergy. An elimination diet can change its life.

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