What Is Fatty Acid Deficiency in Dogs and Cats? — Symptoms to Supplementation, All in One Place

Skin & CoatQ&AMeongsiljang Veterinary Advisory Board

When fatty acid deficiency occurs, we’ll explain the signs that appear in the skin, coat, and overall body, as well as guidelines for omega-3/6 supplementation and when to visit the vet.

What Is Fatty Acid Deficiency?

Close-up of a pet’s skin showing dry, brittle fur and dandruff

Fatty acid deficiency is a nutritional condition in which the body lacks essential fatty acids—such as linoleic acid, alpha-linolenic acid, and arachidonic acid—leading to compromised skin barrier function, coat health, and immune response. The first sign to watch for is changes in the skin. When you notice a dull, brittle coat along with persistent dandruff, itching, and delayed wound healing, it may not be a simple skin issue but rather an imbalance in fatty acids. Dogs must receive adequate linoleic and alpha-linolenic acids through their diet, while cats also require arachidonic acid.

Why Does It Occur?

Fatty acid deficiencies most commonly arise from stale commercial food, low-fat or low-calorie diets, homemade meals, and malabsorption issues involving the pancreas, liver, or intestines. Dry kibble that has been open for a long time can suffer from quality degradation due to improper storage or insufficient antioxidants like vitamin E, which allows fats to oxidize and reduces levels of essential fatty acids, particularly omega-3s, which are highly susceptible to oxidation. Additionally, using only plant-based oils in homemade diets can lead to an imbalance with excessive omega-6 and insufficient omega-3. Unlike dogs, cats have very limited ability to convert linoleic acid into arachidonic acid, making them more prone to deficiency when animal fats are excluded from their diet.

Checklist of Signals From the Body

A lack of essential fatty acids often shows up in your pet’s skin and coat first. If several of the following signs apply, it’s time to review their nutrition.

Dull, brittle fur: The coat loses its shine and the tips become split.

Dandruff and flaking: White flakes fall off when you pet them.

Chronic itching: Poor response even to allergy treatments.

Hair loss and reduced skin elasticity: Patchy hair loss or noticeably less skin elasticity.

Oily, greasy skin: Over time, the skin and coat become greasy and may develop an odor.

Delayed wound healing: Skin regeneration slows down, and minor injuries take longer to heal.

A veterinarian examining a puppy's fur and skin.

These Symptoms May Not Be Simple Deficiency

If your pet experiences severe hair loss and itching, accompanied by red skin rashes, oozing, or crusting, these symptoms cannot be explained by fatty acid deficiency alone. There may be underlying conditions such as atopic dermatitis, sarcoptic mange, Malassezia infection, hypothyroidism, or Cushing’s disease. If you also notice weight loss, decreased appetite, slow recovery after giving birth, or a sudden increase in eye discharge or tearing, please visit a veterinary clinic within 24 to 48 hours for blood tests and skin scrapings.

Omega-3 vs. Omega-6 at a Glance

Item	Omega-3 (EPA, DHA, ALA)	Omega-6 (Linoleic Acid, Arachidonic Acid)
Main Role	Anti-inflammatory, skin barrier, joint/heart protection	Skin/coat formation, cell membrane composition, immune regulation
Representative Sources	Salmon, sardines, krill, flaxseed oil	Chicken fat, sunflower oil, safflower oil, egg yolk
Deficiency Signs	Chronic inflammation, joint stiffness, cognitive decline	Dull coat, dandruff, delayed wound healing
Intake Guidance	During growth, pregnancy, and lactation, supplementation with long-chain omega-3 (EPA, DHA) is recommended by international nutrition guidelines (NRC)	Excess omega-6 can cause an imbalance with omega-3

The balance between the two fatty acids is important, and since the specific recommended ratio varies depending on the animal's health status and diet composition, consult your veterinarian.

How Is It Diagnosed?

Fatty acid deficiency isn’t diagnosed based on symptoms alone; we also review your pet’s diet history and skin condition. Veterinarians typically check three things. First, we take a detailed dietary history covering the past three months, including the food brand, when it was opened, treats, and any supplements. Second, we perform skin scrapings to test for parasites and fungi, ruling out overlapping causes. Third, if needed, we check thyroid levels, liver and kidney function, and total protein. Veterinary internal medicine textbooks emphasize that nutritional deficiencies should only be diagnosed after other skin diseases have been ruled out.

Home Care Points to Keep in Mind

Changing your pet’s diet won’t bring about recovery overnight. To properly assess the benefits of EFA supplementation, you’ll need to monitor your pet for 6–8 weeks.

Prioritize high-quality complete diets: Use up opened packages as soon as possible and store them in airtight containers.

Fish-based omega-3s: Choose pet-specific products that clearly state EPA and DHA content, and always consult your veterinarian to determine the appropriate dosage based on your pet’s weight and health conditions.

Adjust bathing frequency: Bathe no more than once a week using a hypoallergenic shampoo to protect the skin barrier.

Ensure adequate hydration: Essential for maintaining skin moisture.

If you’re also concerned about joint or patellar issues, check out our guide on how to choose joint supplements for dogs.

A guardian gently brushing their puppy’s fur

How to Choose Supplements Safely

Omega-3 supplements vary significantly by product in terms of purity standards (such as IFOS or GOED certification) and EPA/DHA content. Human-grade products may contain additives harmful to pets, such as xylitol and other sweeteners, and their EPA/DHA ratios may not align with veterinary recommendations for animals. Side effects of essential fatty acid supplements are generally mild, typically limited to occasional digestive upset. If your pet is currently taking anticoagulants, steroids, or nonsteroidal anti-inflammatory drugs, consult your veterinarian before starting supplementation. Cats cannot sufficiently convert plant-based alpha-linolenic acid (such as that found in flaxseed oil), so fish-based EPA and DHA sources are recommended.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

How long will it take for the symptoms to improve?

It takes about 6 to 8 weeks to see the effects after changing your pet’s diet and supplements. Since skin and coat growth cycles take time, improvements will appear gradually. If there’s no improvement after this period, it’s a good idea to consult with a veterinarian to check for other potential causes, such as allergies or hormonal disorders.

Can I share human omega-3 supplements with my pet?

We don’t recommend it. Products containing sweeteners (such as xylitol) are toxic to dogs, and the EPA and DHA ratios differ from those formulated for pets. Please use products specifically designed for pets.

Is giving salmon as a treat sufficient?

Since it can be challenging to maintain a consistent serving size, it’s best to use commercial pet food and supplements as the main diet, reserving salmon as an occasional treat. Always cook raw salmon thoroughly before feeding it to your pet, as it may harbor parasites.

Is plant-based omega-3 sufficient for cats?

No, cats have a very limited ability to convert alpha-linolenic acid into EPA and DHA. They require fish oil-based products, and arachidonic acid must also be supplemented separately from animal fats.

Can omega-3 help with atopy?

Omega-3 fatty acids can help by reducing inflammatory responses and improving epithelial barrier function. When used alongside antihistamines, they may provide a synergistic effect. However, since they are not a standalone treatment, please use them under veterinary guidance and as prescribed by your veterinarian.

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References

[1] National Research Council. Nutrient Requirements of Dogs and Cats. Chapter: Fats and Fatty Acids

[2] MacDonald, M. L., Rogers, Q. R., Morris, J. G. Effects of linoleate and arachidonate deficiencies on reproduction and spermatogenesis in the cat. Journal of Nutrition 114:719-726, 1984

[3] Roudebush, P. Consumption of essential fatty acids in selected commercial dog foods compared to dietary supplementation: An update. Proceedings 16th Annual AAVD ACVD meeting, 2001