Mullein leaves come from the flowering mullein plant, scientifically known as Verbascum thapsus L. Although modern medical research on the effectiveness of mullein is lacking, it has been used in traditional medical systems for many purported benefits, especially for ailments involving the respiratory tract. The only modern research on mullein that has been done was in test tubes, so its benefits for the human body have not been confirmed.
According to a study published in "Evidence-Based Complementary and Alternative Medicine" in 2011, mullein leaf is traditionally used as an expectorant because it helps expel mucus from the chest. Its expectorant and anti-rheumatic properties cause you to cough and expel mucus from the lungs and throat. It also lubricates your lungs and throat membranes while reducing swelling, which can help alleviate irritation. Mullein has been traditionally used to remedy bronchitis, asthma, croup, whooping cough, pneumonia, asthma and tuberculosis.
Bacteria and Parasites
A study published in the "Journal of Ethnopharmacology" in 2002 tested the anti-bacterial activity of mullein leaf extract. The study found that mullein has anti-bacterial activity against Klebsiella pneumonia, E. coli, and Staphylococcus aureus and epidermidis -- two types of bacteria found in the lungs and on skin. Another study, published in "BMC Complementary and Alternative Medicine" in 2012, found that mullein leaf extract also kills roundworms and tapeworms in vitro. These anti-bacterial and anti-parasitic activities have not been tested in humans, however.
The same study published in 2012 found that mullein leaf has anti-tumor capabilities. This was only seen in test tubes, however, and there hasn't been research done on the anti-cancer activities of mullein in humans. In the study, growth of tumors induced in potatoes were inhibited by mullein leaf extract. According to the Natural Medicines Comprehensive Database, mullein has also traditionally been used for diarrhea, stomach bleeding, migraines and gout. But studies have not confirmed the effectiveness of mullein in treating these ailments.
Safety and Precautions
According to the Natural Medicines Comprehensive Database, reliable safety information on mullein leaf is lacking. But research has found that mullein is toxic in very large doses. Avoid taking it if you're pregnant or breast-feeding. Consult your doctor before consuming mullein if you're on any medications or using any other herbs because mullein leaf may have interactions with them.