This question has several aspects. One is the safety of the individual herbs imported into this country from other countries. All herbal imports, both raw herbs and prepared herbs, are required to be inspected and cleared by the U.S. Food and Drug Administration before they can be released to purchasers in this country. The FDA collects samples and sends them at random to non-government testing laboratories. All legitimate herb-import businesses should be able to provide documentation of the origin of their herbs and certification of FDA inspection. You can always ask your practitioner if s/he has researched the origin of the herbs s/he is prescribing.
Although Chinese herbs are not as powerful or as likely to produce side effects as most Western drugs, they are still a form of drug therapy and need to be treated seriously. It is generally not advisable to take any drug or herbal product just because it worked for somebody else. When prescribed by a qualified, professionally-trained practitioner of Chinese medicine, Chinese herbal formulas are both safe and effective. A practitioner needs to assess your condition in person before being able to prescribe herbal therapy. Chinese herbs are used safely by pregnant women, and there are a number of pediatric formulas designed to be used by children.