Plants have been used in medicine for thousands of years. Our ancestors used local plant life to treat a number of illnesses, and plants are still used today in many nonindustrial countries as a substitute for modern drugs, which are often prohibitively expensive.
Many of the chemical compounds that occur naturally in plants, called phytochemicals, have beneficial medical effects when consumed by humans. By isolating and processing these phytochemicals, drug manufacturers have been able to create a wide range of complex and effective cures. In fact, 25% of all prescription drugs used today are based on phytochemicals found in plants.
Indeed, many plants hold the key to fighting incredibly serious diseases. Chemicals in foxglove, for instance, have been used to create a drug for treating patients with heart conditions. Similarly, the opium poppy has been used to create morphine, considered by many to be one of the world's most useful pain relievers.
So why is the use of herbal medicine often criticized as being ineffective or unreliable? One of the biggest factors might be that often great claims are made for plants that, while they may have medical uses, don't live up to the hype. Foxglove is a case in point. It was once used as a treatment for many illnesses, including epilepsy, for which it was completely useless. Burdock, a widespread, thistlelike plant, is another. Though it is an effective cure for minor skin irritations caused by stinging nettles and poison ivy, claims for it being able to cure cancer, AIDS, and diabetes are completely unproven.
Medicinal plants may also contain side effects or dangers that are not always known to the recipient. Rosy periwinkle, which has been used in Chinese and Indian medicines for centuries and apparently heals ailments as diverse as diabetes and constipation, is in actuality highly toxic. In addition, due to varying environmental factors, two different specimens of the same herb may have widely different strengths—a factor that is difficult to predict and that can make prescribing the correct dosage a matter of perilous speculation.
This is not to say that taking herbal remedies cannot be effective. However, just as you would with prescription drugs, you should consult a medical professional before you take any.