Mullein tea is generally considered safe for most adults, but several groups of people should avoid it. Those include pregnant and breastfeeding women, people with kidney disease, anyone with known plant allergies in related families, and young children. The risks are less about dramatic toxicity and more about gaps in safety data and a few specific biological concerns worth understanding.
Pregnant and Breastfeeding Women
There is no reliable safety data on mullein use during pregnancy or breastfeeding. Without studies confirming it won’t affect fetal development or pass problematic compounds through breast milk, the standard guidance from both WebMD and clinical references is straightforward: avoid it entirely. This isn’t because harm has been documented, but because no one has confirmed it’s safe, and herbal teas can contain bioactive compounds that behave unpredictably during pregnancy.
People With Kidney Disease
If you have kidney problems, mullein tea deserves extra caution. Research has linked mullein to at least one case of acute kidney failure when it was used as part of an herbal cleansing blend (a product called CKLS that combined mullein with aloe, chamomile, cascara sagrada, chaparral, and several other herbs). It’s difficult to isolate mullein’s exact role in that case since it was one ingredient among many, but the association was enough for health sources like Everyday Health to recommend that people with kidney disease either avoid mullein entirely or clear it with their doctor first.
The concern makes biological sense. Your kidneys filter everything you consume, and when they’re already compromised, even mild additional stress from herbal compounds can tip the balance. If your kidney function is reduced for any reason, whether from chronic kidney disease, diabetes-related kidney damage, or a single functioning kidney, this is a tea to skip.
People With Plant Allergies
Mullein belongs to the figwort family (Scrophulariaceae), and some people develop contact dermatitis, an itchy skin rash, just from handling the plant. If you’ve ever had a skin reaction to mullein or related plants, drinking a concentrated tea made from the leaves is not a good idea.
Beyond direct allergy, cross-reactivity is worth considering. If you’re sensitized to birch pollen, olive pollen, or plants in the Rosaceae family (which includes strawberries, peaches, and apples), your immune system may react to proteins that share structural similarities across plant species. While mullein-specific cross-reactivity studies are limited, people with multiple pollen sensitivities tend to be more reactive to a broader range of herbal products. If you have a history of oral allergy syndrome, where raw fruits or certain teas make your mouth tingle or swell, approach mullein tea cautiously.
Children
No established safety guidelines exist for giving mullein tea to children. Pediatric dosing for herbal products is rarely studied, and children’s smaller body weight means any bioactive compound hits harder per pound. The lack of data alone is reason enough to keep mullein tea away from young kids. Some parents encounter mullein ear oil marketed for children’s ear infections, but that’s a topical product, not an ingested tea, and even those products lack rigorous pediatric safety testing.
People Preparing for Surgery
Many health organizations recommend stopping all herbal supplements two to three weeks before any scheduled surgery. This applies to mullein tea as well. Herbal compounds can interact with anesthesia, affect blood clotting, or alter how your body processes surgical medications in ways that aren’t always predictable. If you have a procedure coming up, put the mullein tea on hold and let your surgical team know about any herbal products you’ve been using.
Anyone Drinking Unfiltered Mullein Tea
This one applies to all mullein tea drinkers, not just specific groups. Mullein leaves are covered in fine, tiny hairs that can irritate your throat and digestive tract if they end up in your cup. This isn’t an allergic reaction. It’s a mechanical irritation, like swallowing tiny fibers. Before drinking mullein tea, strain it through a fine mesh strainer or cheesecloth to remove as many plant particles as possible. If you skip this step, you may end up with a sore, scratchy throat that defeats the purpose of drinking the tea in the first place.
A Note on Mullein Seeds
Mullein tea is made from the plant’s leaves and sometimes its flowers, but the seeds are a different story entirely. Mullein seeds contain rotenone, a compound that interferes with how your cells produce energy at the mitochondrial level. In acute exposure, rotenone causes nausea, vomiting, diarrhea, and in severe cases, dangerous drops in blood pressure and impaired heart and lung function. Commercially sold mullein tea should not contain seeds, but if you’re harvesting mullein yourself to make tea, be careful to use only the leaves and flowers. The seeds have historically been used as a fish poison, which gives you a sense of their potency.
People on Medications
Formal drug interaction studies for mullein are essentially nonexistent. Published pharmacological reviews have found no reported interactions, which sounds reassuring but really just means no one has looked hard enough. The absence of evidence is not the same as evidence of safety. If you take medications that are sensitive to changes in kidney function, blood clotting, or liver metabolism, the safest approach is to talk to your pharmacist before adding mullein tea to your routine. This is especially relevant if you take blood thinners, blood pressure medications, or drugs with a narrow therapeutic window where small changes in how your body processes them could cause problems.