What is garlic?
Garlic, the bulb of the plant Allium sativum, is a well-known herb and food flavoring substance. As a supplement, it may be administered in its raw form as the fresh bulb, as an oil or a liquid alcohol extract, or as a dried powder in gelatin capsules.
Why recommend administration of garlic to my pet?
Herbalists recommend the use of garlic as an antibacterial or antifungal agent, and to lower blood lipids and cholesterol in people. It is also used in an attempt to lower blood pressure and inhibit tumor formation. Many of these uses are not substantiated in clinical testing.
In pets, garlic is often recommended to decrease internal and external parasites. Flea control products for dogs and cats that utilize garlic abound on pet supply store shelves.
How much experience is there with the use of garlic in pets?
Garlic has been used in products for flea control in dogs and cats for many years.
How much research has been conducted on this supplement?
Despite the abundance of products that utilize garlic as a method of flea control in dogs and cats, research supporting its efficacy is lacking. There are some anecdotal reports of an anti-parasitic effect of garlic in dogs and cats.
"Despite the abundance of products that utilize garlic as a method of flea control in dogs and cats, research supporting its efficacy is lacking."
A minimal amount of research suggests that garlic may be effective in killing Giardia (an intestinal protozoan parasite) and dermatophytes (e.g. ringworm fungus) in dogs and cats. It also appears that garlic may reduce blood pressure in dogs and help minimize aminoglycoside (a particular type of antibiotic) toxicity in many species. Some laboratory studies have illustrated an ability of garlic to inhibit tumor formation and lower blood pressure.
"...these effects must be considered marginal..."
All of these effects must be considered marginal, and weighed against the potential for garlic to damage the red blood cells of dogs and cats.
How safe is garlic?
Garlic may increase insulin secretion in type I diabetes and should probably be researched for potential benefits to diabetic dogs. Meanwhile, it should be used carefully in diabetic animals receiving insulin therapy. Garlic also may delay blood clotting and enhance the action of anticoagulant medication. It should not be used in animals with bleeding disorders.
"...the use of garlic in dogs and cats...resulting in damage to red blood cells..."
The most important concern surrounding the use of garlic in dogs and cats is its ability to induce oxidative stress, resulting in damage to red blood cells, placing the animal at risk for anemia. Larger doses are likely required for this effect, and garlic can probably be used safely at low levels provided red blood cell parameters are routinely evaluated. Concurrent administration of anti-oxidants may also protect against the red blood cell damaging effects of garlic.
Where do I obtain garlic and do I need a prescription?
Pet owners are cautioned against buying supplements without knowledge of the manufacturer, as supplements are not highly regulated and some supplements may not contain the labelled amount of ingredients. A prescription is not needed for garlic. Your veterinarian may have preferred supplements that he or she will recommend.