If there's an adverse reaction, other herbs with similar properties can be tried. Side effects from herbs are less common than side effects from drugs and usually less severe. If an herb disturbs the digestion, it may be that the body is learning to process it. Give it a few more tries before giving up. Stop taking any herb that causes nausea, dizziness, sharp stomach pains, diarrhea, headache, or blurred vision.
Slippery elm is an excellent antidote to any type of poison.
If you are allergic to any foods or medicines, it is especially important to consult resources that list the side effects of herbs before you use them. Understand that different preparations of the same herb can work differently. The safety of any herbal remedy is dependent on the way it is prepared and used. Tinctures and extracts contain the alkaloids, or poisonous, parts of plants and need to be used with care and wisdom. Dried herbs made into teas or infusions contain the nourishing aspects of the plants and are usually quite safe, especially when nourishing or tonifying herbs are used.