Moreover, not all plant life is beneficial. There are poisonous plants, and some of them are deadly, especially if used for long periods of time. In fact, it is important to point out that qualified herbalists use herbs with great care. Also, since herbs contain active ingredients, one should be aware that some of these elements may interact negatively with prescribed medications. Certain herbs should be used only for healing purposes, and not for extended periods of time.
Herbs can be of great value when used in a program of self-care and preventive medicine.
But because they vary in strength from gentle remedies that can be eaten like food to potential lethal poisons, medicinal plants should always be used under the supervision of a Health Care Professional. Herbal therapy has been criticized because medicinal plants have not been tested for efficacy according to rigid pharmaceutical standards. However, there's continuing debate over whether such testing should be performed on the entire herb or only on its active ingredients. Another problem is that sometimes an herb's active ingredients are not known. Proponents of herbal therapy point out that the pharmaceutical industry grew out of herbal treatment and that plant extracts are still used to make drugs.