Can an herb or supplement improve your sex life? The market is flooded with herbal products whose manufacturers claim they can, but consumers should treat these claims with skepticism.

Most of the creams and herbal supplements available over the counter and sold on the Internet have not been studied rigorously. Since the FDA doesn't regulate the use and dosage of herbal products, their safety and effectiveness are unknown. Dosages can vary widely from product to product and even pill to pill. Keep in mind, too, that "natural" doesn't mean harmless. Herbal products can cause side effects and interact with other medications.

Also, what's listed on the label is not necessarily what's inside the bottle. This is illustrated by a 2006 FDA warning that urged consumers to avoid the following dietary supplements that claim to treat erectile dysfunction and improve sexual performance: Zimaxx, Libidus, Neophase, Nasutra, Vigor-25, Actra-Rx, and 4EVERON. The FDA found that these products contained sildenafil, vardenafil, or substances that are nearly identical to these medications. But none of these chemicals were listed on the products' labels. In fact, the packaging was misleading. According to the FDA, the packaging claimed that the products were "all natural" and did not contain the active ingredients used in FDA-approved erectile dysfunction drugs.

This poses a serious health risk to consumers who might take such a product unaware that it could interact with other medications. Like sildenafil or vardenafil, the chemicals in these supplements can interact with nitrates (which are commonly used to treat angina and congestive heart failure) and cause blood pressure to drop to dangerously low levels.

There is a dizzying array of other products marketed for improving sexual function. The chart below examines a handful of commonly known alternative therapies. But medical experts agree that it's best to opt for well-tested, FDA-approved medications. If you do decide to use an alternative therapy, tell your doctor about it so he or she can watch for possible side effects and drug interactions.