Since cats often like to chew plants, owners should check to see if a particular herb is toxic to cats before purchasing it. Many herbs can cause all sorts of digestive and blood problems that can lead to coma or even death in cats.
Alfalfa, reishi and shitaki mushroom and chamomile all have blood thinning effects on cats, which can be harmful for cats with blood problems.
Bilberry, dandelion, ginkgo biloba, ginger, fever few, and garlic can lower a cat's blood sugar level, which is bad for cats with gallbladder problems.
Blood pressure in cats can be raised or lowered with ginseng, hawthorn berry and licorice.
Liver and Kidney Damage
A large number of herbs can cause liver and kidney damage in cats including boswellia, cayenne, lavender, celery seed, yellow dock, borage, colt's foot, comfrey, chaparral, golden seal, kava kava and oregon grape. These herbs should be avoided by all cats.
Ulcers and other digestive problems can be caused by cayenne, kava kava, valerian, sarsaparilla, licorice, aloe, senna, turkey rhubarb, St. John's wort, black walnut hulls, boswellia, burdock root and chickweed.