Fish Oil for Dogs - Benefits and Side EffectsWe know that it’s beneficial to humans, but what about fish oil for dogs?

Fish oil has become the most popular supplement among people a long time ago, mostly due to its robust scientific profile supporting major health benefits for humans.

Today, fish oil supplements are expanding into the animal and pets market, particularly those for dogs. Majority of companies claim that fish oil can help with canine arthritis.

We’ve already talked about the side effects and benefits of fish for dogs, but what about supplements of fish oil for dogs? Do they work? Are there any side effects? Let’s take a quick look.

What is fish oil and its supplements?

Most commercially available fish oil supplements are derived from fish that live in colder waters, primarily menhaden, but also herring, salmon and trout.

Fish oil is extracted for supplements which can be purchased for your dog as edible capsules, chewable tablets or liquid products.

Fish oils are rich in fatty acids, particularly two classes, the omega-3’s and the omega-6’s.

In humans, omega-3 fatty acids are associated with a reduced risk of cardiovascular disease, decreased adverse events in people with heart disease, and benefits for patients with inflammatory disorders such as rheumatoid arthritis.

Fish obtain their omega-3 fatty acids from algae. This means algae may become the dominant source of omega-3 fatty acids as fish populations continue to decline in the world’s oceans.

Omega-3 fatty acids include:

  • Eicosapentaenoic acid (EPA)

Omega-6 fatty acids include:

  • Arachidonic acid (AA)
  • Docosahexaenoic acid (DHA)
  • Linoleic acid (LA)
  • Alpha-linolenic acid (ALA)
  • Gamma linolenic acid (GLA)
  • Dihomo-gamma-linolenic acid (DGLA)

There is a third class of fatty acid which is sometimes mentioned, the omega-9 fatty acids.  These decrease the concentrations of omega-3 and omega-6 fatty acids in the blood and skin.

Benefits of fish oil for dogs

Fish Oil for Dogs and Pets - Benefits and Side Effects

Initially, fish oil was used as a supplement for dogs to treat canine allergies. However, it is now recommend by veterinarians for a wide variety of conditions ranging from kidney disease to arthritis and high cholesterol.

Some owners of perfectly healthy dogs add fish oil to their pets’ food at every meal for general health maintenance.


Fish oil supplementation may be helpful for pets with a range of inflammatory diseases including diseases of organs such as the heart and kidneys, arthritis of joints, allergies and some cancers.

The eicosapentaenoic acid and docosahexaenoic acid in fish oil are converted into prostaglandins which are powerful hormone-like substances. In this case, they are turned into series 3 prostoglandins which reduce the tendency of tissues to become inflammed.

In contrast, the omega-6 fatty acid, AA (commonly found in animal fat) is converted into series 2 prostaglandins. This group of prostoglandins promote inflammation.

The higher the ratio of omega-3 fatty acids to AA in the diet, the less prone an animal will theoretically be to developing inflammatory disorders – hence, the recent interest in the ratio of omega-3 to omega-6 fatty acid in fish oil supplements.

Unfortunately, commercial dog foods tend to be very low in omega-3 fatty acid content meaning that dogs fed these diets may become predisposed to inflammatory disease.

Other inflammatory-related diseases may respond to the anti-inflammatory effects of certain fatty acids, especially EPA.

In severe inflammatory diseases, fish oil supplement will not suffice on its own, but may boost the effects of other therapeutics.

Allergies and autoimmune conditions

Allergies and autoimmune conditions are due to the over-reaction of the immune system. The harmful effects of these diseases can be reduced by some fatty acids.

Some researchers have suggested that fatty acid supplements may be useful to prevent allergies to inhaled substances such as pollens and molds from developing in young animals.

Fish oil supplement can help relieve the itching of allergy-related skin conditions such as atopic dermatitis.

Dull and dry hair coat

If your dog has a dull, brittle or dry coat, it may respond to supplementation with essential fatty acids, especially LA, contained in fish oil.

It has also been found that in some cases of dermatitis, there is a deficiency of LA in the skin. In these cases, supplements high in LA can be useful.

The addition of EPA and GLA may also be beneficial as they would help reduce the release of AA from cells damaged because of the skin condition.

Yeast infections

Fatty acids slow the growth of Malassezia pachydermatis, a common yeast infection on the skin and in the ears of dogs.


The proper development of your dog’s retina and visual nervous system is dependent on omega-3 fatty acids, so these may be particularly important for bitches in late pregnancy and also for puppies.

Heart and vascular problems

Omega-3 fatty acids may prevent some cardiac problems. In dogs, these have prevented conditions causing an irregular heart beat and reduced high blood pressure.

Animals prone to blood clots may be helped by the anti-clotting effect of fatty acids.


Omega-3 fatty acids have been shown to slow the development of some cancers; in contrast, omega-6 fatty acids may stimulate tumor development.

Plasma triglycerides and cholesterol

Fish oils have been shown to decrease levels of lipids and cholesterol in the blood.

Animals receiving therapy with synthetic vitamin A for various skin problems may develop elevated levels of lipids in the blood (hyperlipidemia); fish oil supplement may benefit dogs suffering from this condition.


Omega-3 reportedly has a calming effect on some nervous dogs.

Synergistic effects

Omega-3 fish helps antihistamines and glucosteroids work more effectively.

This cooperative effect means your dog can take lower doses of these medicines.

Side effects of fish oil for dogs

At high doses, the most serious adverse effect of over-supplementing fish oil in dogs is inflammation of the pancreas (pancreatitis), although this is rare.

Pancreatitis can cause abdominal pain, vomiting, diarrhea which can lead to dehydration.

Omega-3 fatty acids have anti-clotting effects beneficial for cardiovascular problems. However, over-supplementing can lead to increased and prolonged bleeding.

Dogs with bleeding disorders should not take omega-3 fish oil without veterinary approval.

Some dogs given fish oil may develop ‘fishy’ breath, oily hair or yellow skin flakes.

In other animals

In humans (and therefore potentially dogs), the most common negative effects of fish oil are gastrointestinal. These effects can include a fishy aftertaste, bad breath, burping, heartburn and abdominal bloating and pain.

High doses of fish oil may cause nausea, loose feces and diarrhea. A reduction in the inflammatory response can decrease the effectiveness of the immune system.

In rats, the immune system can become suppressed with daily doses as low as 0.9 g EPA and 0.6 g DHA.

Small decreases in blood pressure can also occur when taking omega-3 fatty acid supplements.

Omega-6 fatty acids may encourage tumor development.

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