Echinacea is generally considered safe when used under supervision. In the older literature, there is a warning not to use this herb for certain immune disorders (autoimmune diseases, diabetes) and disorders with diminished immune systems with low white blood cell counts (feline leukemia and immunodeficiency diseases.) However, echinacea has been used in these instances without obvious harm. Generally, echinacea is not meant for long term use and most doctors limit its use to a few months at a time.

Garlic is a favorite herb used by many pet owners to control fleas, ticks, mosquitoes, and other insects. While many of my clients swear by the ability of garlic to control fleas, and while I have no problem recommending its use, controlled studies have shown garlic to be ineffective as an insecticide. Garlic also has show antimicrobial and anti-cancer properties. Garlic can cause anemia in dogs and cats due to the presence of S-methyl cysteine sulfoxide and N-propyldisulfhide. Therefore, it should not be used in pets with anemia. As a general guideline, 1 clove of garlic per 10 pounds of body weight for dogs (and 1/2 clove per cat) can usually be fed safely each day. If you use garlic regularly (as a general food supplement,) it would be wise to have your pet's blood checked every few months to make sure anemia is not occurring.

Ginkgo is a well-known and popular herb that has a number of uses. It is best known as a supplement that may improve cognitive disorder in aging people and pets, particularly in those with mild dementia (Alzheimer’s in particular.) While its ability to prevent blood clots can be beneficial in certain cases, a well-known side effect of ginkgo is increased and potentially serious bleeding problems. In people, bleeding (including fatal brain hemorrhages) have been reported when ginkgo was combined with high doses of fish oil or other anticoagulants.