# Pharmacological question: Side effects of nettle tea? Catnip marshmallow and fennel tea? **URL:** \ **Category:** Factual Questions\ **Created:** [December 29, 2019, 12:33am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529 "2019-12-29T00:33:34Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [December 29, 2019, 12:33am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/1 "2019-12-29T00:33:34Z")
Mrs P came home from a shopping trip with packages of “Mint & Nettle tea”, and also “Mint, Catnip, Marshmallow and Fennel tea.” Both of them have the same warning on the label: “Do not take while pregnant or breastfeeding or if taking any other medications.” Both packets say “keep out of reach of children”. The phrase “if taking any other medications” seems pretty broad to me. And why the caution about keeping out of reach of children? Do any of these herbs have interactions with other meds we should be concerned about? Not my pharmacist, etc. But curious why warnings like this on herb tea. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [December 29, 2019, 1:48am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/2 "2019-12-29T01:48:16Z")
> [@Northern\_Piper](#): > > Mrs P came home from a shopping trip with packages of “Mint & Nettle tea”, and also “Mint, Catnip, Marshmallow and Fennel tea.” > > Both of them have the same warning on the label: “Do not take while pregnant or breastfeeding or if taking any other medications.” Both packets say “keep out of reach of children”. > > The phrase “if taking any other medications” seems pretty broad to me. And why the caution about keeping out of reach of children? > > Do any of these herbs have interactions with other meds we should be concerned about? > > Not my pharmacist, etc. But curious why warnings like this on herb tea. [http://pennstatehershey.adam.com/content.aspx?productid=107&pid=33&gid=000275](http://pennstatehershey.adam.com/content.aspx?productid=107&pid=33&gid=000275) \* "The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs can trigger side effects, and can interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a health care provider. Stinging nettle is generally considered safe when used as directed. Occasional side effects include mild stomach upset, fluid retention, sweating, diarrhea, and hives or rash (mainly from topical use). It is important to be careful when handling the nettle plant because touching it can cause an allergic rash. Stinging nettle should never be applied to an open wound. Because nettle can alter the menstrual cycle and may contribute to miscarriage, pregnant women should not use nettle. DO NOT self treat with nettle for BPH. See your doctor to receive a diagnosis and to rule out prostate cancer. There is some evidence that stinging nettle may raise blood sugar and interfere with diabetes management. There is also evidence that it can lower blood sugar. Patients with diabetes should monitor their blood sugar closely when using stinging nettle. Stinging nettle can have a diuretic effect. If you have kidney or bladder issues, speak with your provider."\* > **[Fennel: Side Effects, Uses, Dosage, Interactions, Warnings](https://www.rxlist.com/fennel/generic-drug.htm)** > > Fennel is an herbal supplement that can be used as a treatment for infants and nursing children suffering from colic and dyspeptic disease. Learn about side effects, drug interactions, dosages, and more. \*Side effects of Fennel include: difficulty breathing tightness of chest/throat chest pain nausea vomiting hives rash itchy or swollen skin mild increase in menstrual flow sun sensitivity Serious side effects of Fennel include: seizures\* But here’s the main thing- they test modern drugs vs other common drugs. They dont for odd herbal stuff, and your Doc or Pharmacist generally dont know you are taking a herbal medication when they prescribe a drug. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [December 29, 2019, 2:21am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/3 "2019-12-29T02:21:23Z")
There is very little governmental control of what is even in these herbal supplements. ---
**Author:** ![Sunny\_Daze](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunny_daze/32/438_2.png) [@Sunny\_Daze](https://boards.straightdope.com/u/Sunny_Daze)\ **Post date:** [December 29, 2019, 2:52am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/4 "2019-12-29T02:52:28Z")
The mint, marshmallow, catnip and fennel sounds relatively innocuous. Fennel and mint are used in cooking. Catnip is also a mint. Marshmallow is used in some cultures for cooking. It acts to soothe mucous membranes and is commonly used for sore throats. ---
**Author:** ![Ca3799](https://avatars.discourse-cdn.com/v4/letter/c/9f8e36/32.png) [@Ca3799](https://boards.straightdope.com/u/Ca3799)\ **Post date:** [December 29, 2019, 3:12am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/5 "2019-12-29T03:12:48Z")
You might could get some information from LactMed, a website focused on meds (and herbals) that can or cannot be passed to infants through breastfeeding. They may list potential effects/side effects of those particular ingredients. [https://www.ncbi.nlm.nih.gov/books/NBK501922/](https://www.ncbi.nlm.nih.gov/books/NBK501922/) There is also a book used by lactation consultants to look up meds and herbals for the same purpose called _Hale’s Medications and Mother’s Milk_. But I think the reason for the warnings is that herbals and nutritional supplements aren’t regulated by the FDA so there won’t be formal research into the possible efficacy or the effects/side effects of herbals and supplements in children, pregnant women, breastfeeding women, with regards to interactions with other drugs or herbals, or with regards to content. There is not usually a listed “dosage” with herbals. It’s just “mint tea” and not “30 mg of ‘mintyness substance’ per serving” tea. Additionally, some nutritional supplements and herbal products make the news pretty regularly for having incorrect dosages listed on the packaging so even when labeled, the label may not be correct. I made and sold homeopathic remedies several years ago (even though I think homeopathy is bull, it is cheap and easy to make!). Homeopathic remedies are similar to herbal and nutritional supplements in that their contents are not regulated. I actually registered my business with the FDA and had my ‘facility’ (AKA my ‘kitchen’) inspected by a nice gentleman from there. As far as I know, I was the only manufacturer of homeopathic remedies who was registered with the FDA (which I tried to use as advertising). I had to be very, very careful about what claim(s) I made when advertising my products. Vague claims that were not specifically health-issue related attracted no attention at all (such as a homeopathic remedy for “releasing of fear” or “releasing of attachments”). “Fear” and “attachment” are not medical diagnoses. Direct diagnostic or specific health-related statements were not allowed (such as “for cold and flu”) unless a disqualifier was added such as “aids with the relief of cold and flu”). ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [December 29, 2019, 7:34am UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/6 "2019-12-29T07:34:15Z")
Some medicinal herbs can be dangerous. I discovered one bad combination myself, as I reported here 6 years ago: > [@Danger, narrowly averted](https://boards.straightdope.com/t/danger-narrowly-averted/668753/7): > > I had an interesting close call about 2 weeks ago I almost started a thread about. My wife made me star gooseberry tea for a headache; a little later I took an isordil sublingual; later still I stood up. … Whoooo! Low blood pressure(??) I thought I was a goner. I lay down, wife asked if I wanted more star gooseberry tea _which I hadn’t connected to the sensation_. I said “Yes … wait, I’ll drink some water first.” > > While drinking the water I recalled that the symptoms were similar to (but worse than) the time I had isordil a few days after a small dose of sildenafil. Using Google, I found some ambiguous comments about remedies in the same Phyllanthus genus as star gooseberry being dangerous for heart patients. (I thought about starting an IMHO thread: “I’ve learned something about Phyllanthus – is it well known?”) > > Had I gone ahead and drunk some more star gooseberry tea, it might have been MUCH worse than a double dose of sedative. ---
**Author:** ![Treppenwitz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/treppenwitz/32/3445_2.png) [@Treppenwitz](https://boards.straightdope.com/u/Treppenwitz)\ **Post date:** [December 29, 2019, 2:16pm UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/7 "2019-12-29T14:16:25Z")
> [@DrDeth](#): > > …But here’s the main thing- they test modern drugs vs other common drugs. They dont for odd herbal stuff, and your Doc or Pharmacist generally dont know you are taking a herbal medication when they prescribe a drug. Very true; and on a more fundamental level, if you develop a new drug, you’re supposed to know what its mechanism of action is and what its metabolic pathways are; so that when it comes to interactions with other drugs you know what to look out for and which drugs/classes are most important to investigate for potential interactions. You may well have incomplete (or even no) information for an old herbal remedy’s mechanism of action and metabolic pathways. That can make it hard to even guess at potential problems, especially for the more obscure herbals. FWIW it does look as if some information for fennel is googleable. j ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [December 29, 2019, 4:17pm UTC](https://boards.straightdope.com/t/pharmacological-question-side-effects-of-nettle-tea-catnip-marshmallow-and-fennel-tea/845529/8 "2019-12-29T16:17:35Z")
> [@Ca3799](#): > > But I think the reason for the warnings is that herbals and nutritional supplements aren’t regulated by the FDA so there won’t be formal research into the possible efficacy or the effects/side effects of herbals and supplements in children, pregnant women, breastfeeding women, with regards to interactions with other drugs or herbals, or with regards to content. Lack of/insufficient regulation of herbal products doesn’t prevent “formal research” into their efficacy and potential side effects. Such research has been done and is ongoing into multiple herbs and their active ingredients. That’s how we got (to cite just a few examples) aspirin, digoxin and Taxol. [Here’s](http://ncbi.nlm.nih.gov/pubmed/26325431) an example of published research that cites potential hazards of some herbal products in pregnant women. “Nutritional supplements” have $30 billion+ in sales annually in the United States alone. There’s plenty of money there to conduct large-scale clinical studies of herbal drugs (big pharma firms produce a lot of these products). What’s lacking is the incentive to do so. Why risk finding out that your big moneymakers are useless, when the government lets you claim how great they are without supporting evidence? Just put a Quack Miranda Warning on the bottle (“This product is not intended to diagnose, treat, cure or prevent any disease.”) and maybe a pregnancy use advisory to cover your ass, and bingo! Profit.