Mehmet Oz, M.D., is host of “The Dr. Oz Show,” and Mike Roizen, M.D., is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. Email questions to youdocsdaily@sharecare.com.

QUESTION: I heard that a natural extract from daffodils — an essential oil, I think — has cancer-killing properties. Is that true?

— Gregory F., Urbana, Illinois

ANSWER: Plant-derived essential oils and other substances that have a profound effect on human physiology are in the news lately, as researchers look for less-toxic and more-effective therapies for everything from diabetes and cancer to depression and autoimmune diseases.

In fact, the National Cancer Institute has screened approximately 35,000 plant species for potential anti-cancer activities and found 3,000 species with reproducible anticancer activity. Isolation of several compounds from the mayapple, for example, ultimately led to the development of drugs that treat testicular and small cell lung cancer.

As for daffodils, new research has tested the anti-cancer properties of an extract from that flower called hemanthamine. It appears that down the road, its anti-cancer properties may be tested in clinical trials.

But that does NOT mean you should use daffodil extract/essential oil in hopes of battling or preventing cancer.

Some extracts of plant-derived substances can be lethal if ingested or absorbed through the skin. For example, ingesting wintergreen oil is potentially health- and life-threatening. Furthermore, online extracts are generally NOT regulated. There’s no way to know what you’re getting (contamination or deception often add to the risk). Be careful of exposure to compounds such as phthalates, which they may contain.

A study presented at ENDO 18, the Endocrine Society’s 100th annual meeting in Chicago, reveals a potential link between abnormal breast growth in young boys and regular exposure to hormone disruptors in lavender and tea tree oils in consumer products.

However, for most adults, essential oil aromatherapy (using only essential oils like lavender) can help you sleep, feel less anxiety in an MRI or relieve pain.

So be smart about your use of essential oils and other extracts. You don’t want to end up needing conventional medical intervention because of a “natural therapy.”