FAQ: Frequently Asked Questions

There are important contraindications that apply to using Nettle™. If any of the below contraindications apply to you, you should not use Nettle™.

• Persons who are under 18 years old.
• Persons with a history of seizures or epilepsy.
• Persons who are pregnant or may be pregnant. Note: if you are trying to conceive, or conceive accidentally, Nettle™ will not interfere with your hormones or chances, and there are no known side effects of women using the technology underlying Nettle™ in the first trimester.
• Persons experiencing active suicidal thoughts.
• Persons with a pre-existing neurological condition.
• Persons with a lesion, tumour or other defect in your skull, cranium or brain.
• Persons with an implant inside their skull, cochlear implant or implanted hearing aid.
• Persons with implanted medical devices, such as a cardiac pacemaker or neurostimulation devices, such as spinal cord stimulators, vagal nerve stimulators, auricular stimulators, or deep-brain stimulating electrodes. Note: external/non-invasive stimulators will not interfere with Nettle™'s efficacy or safety, but it is recommended not to use them at the exact same time.

If you are unsure about whether any contraindications apply to you, you must consult with your physician before continuing, especially if you are under the care of a physician for any conditions related to the central nervous system (e.g. neurology).

Your brain naturally runs on electricity, and neurons, the main cells in the brain, communicate using electrical signals called action potentials. Nettle™ uses the natural language of neurons to help rearrange and regenerate neural pathways - a process known as neuroplasticity.

This is done by administering safe and small electrical pulses to brain regions where these fluctuations occur. We are able to target them via the placement of the electrodes on the headband, one targeting your dorsolateral prefrontal cortex (DLPFC) and the other targeting your insula via your motor cortex (M1). During your luteal phase, fluctuations occur in these specific brain regions which contribute to symptoms of PMS and menstrual pain such as low mood, anxiety, brain fog and cramps.


This stimulation gets neurons firing in a way that is more consistent with follicular phase activity, empowering you to feel your best even during the premenstrual phase. The technology Nettle™ employs is well-known and validated from the fields of depression and chronic pain treatment, and is known as transcranial direct current stimulation (tDCS).

Yes, extensively. We have run more than three years of tests on Nettle™ itself, and this builds on decades of research into the underlying neurotechnology and its mechanisms. These tests range across safety, efficacy, ergonomics, and more. The results of our WIND trial are available on the Nettle page, and demonstrate significant improvement in low mood, pain and function after using Nettle for just 5 days, which is equivalent to one cycle. We are in the process of setting up and conducting more trials, including one with the NHS that will test the efficacy of Nettle™ amongst patients with endometriosis and other trials for PMDD, among other conditions.

Nettle™ is designed to help manage a variety of physical and psychological symptoms. Physical symptoms include menstrual pain and cramping, while psychological symptoms encompass low mood, irritability, anger management, mood instability, and brain fog. There is stronger evidence supporting Nettle™'s effectiveness for certain symptoms compared to others.

The technology behind Nettle™ has been rigorously tested in multiple clinical trials and continues to be assessed in ongoing studies to evaluate its effectiveness across various clinical endpoints.

The physical and psychological symptoms that Nettle™ is designed to address all manifest as brain activity. Nettle™ has different modalities that target different brain regions. One, aimed at addressing physical symptoms via the Motor Cortex (M1), is designed to target the way the brain reacts to and processes pain signals. The other, aimed at addressing psychological symptoms via the Dorsolateral Prefrontal Cortex (DLPFC), is designed to modulate the way the brain’s cognitive centres work.

Yes, Nettle™ has been rigorously tested for safety, and its underlying technology is supported by over 30 years of evidence demonstrating its safety for both short- and long-term use. However, as with all medical technologies, Nettle™ may not be suitable for everyone. The key contraindications for using Nettle™ are diagnoses and history of epilepsy and/or seizures, and any pre-existing neurological implants, which could interfere with its mechanism of action.

Nettle™ is not designed to cure PMS, PMDD, dysmenorrhea, or any other women’s health condition. However, Nettle™ is a therapeutic that improves a range of physical and psychological symptoms that are commonly experienced by people diagnosed with such conditions. In our clinical trials, Nettle™ was proven to improve low mood, pain and functionality in our users, which are common symptoms of those struggling with menstrual health conditions.

No, Nettle™ does not have any direct impact on the hormone levels in your body and will not affect your menstrual cycle. The physical and psychological symptoms that Nettle™ is designed to address all manifest as brain activity in the dorsolateral prefrontal cortex and motor cortex.

Nettle™ is controlled through the Samphire mobile application on your phone, using Bluetooth connection. The Samphire application will be available to download on the Apple and Google app stores. It will give you full control over Nettle™ and help you see your progress over time. The application integrates with cycle tracking, allowing you to create personalised schedules and routines, learn about symptoms over time, and improve predictability.

Yes! Nettle™ is safe to bring in your carry-on luggage. Users have travelled with it without any issues, and there are no restrictions on taking it through airport security. For a smooth screening process, we recommend placing it in a tray with your other small electronics and making sure that the water bottle is emptied (the water bottle capacity is 60 ml).

Nettle has not yet been tested on exclusively PCOS patient populations and we have not run trials specifically including only women with a diagnosis of PCOS. However, Nettle™ has been designed specifically with women in mind who have certain types of PCOS symptoms; and it may be worth exploring as an option alongside other treatment options.

If you do have PCOS and use Nettle™ to manage your mood or pain symptoms, please make sure you start running sessions daily, a few days prior to the expected start of your symptoms, up to 20 days in a row. While you could use Nettle™ more, most people will notice a difference within this period of time, and additional sessions are not necessary, but maintaining a regular schedule (use Nettle™ again after taking a 5-10 day break).

Premenstrual dysphoric disorder (or PMDD) is a serious condition that - like much of women’s health - has been largely ignored by research, clinicians and solutions for too long. PMDD is a complex condition, with complex symptomatology, and women with PMDD do not necessarily have the same symptoms or experiences.

Nettle™ has been designed specifically with women in mind who have certain types of PMDD symptoms, especially low mood; and it may be worth exploring as an option alongside other treatment options. Nettle™ has not yet been tested on exclusively PMDD patient populations, and we’re currently investigating such benefits in a separate clinical trial.

If you do have PMDD and use Nettle™ to manage your mood or pain symptoms, please make sure you start running sessions daily, a few days prior to the expected start of your symptoms, up to 20 days in a row. While you could use Nettle™ more, most people will notice a difference within this period of time, and additional sessions are not necessary, but maintaining a regular schedule (use Nettle™ again after taking a 5-10 day break).

We, like you, are frustrated by the lack of research and effective solutions for chronic women’s health conditions. Endometriosis - experienced by 1 in 10 women - is high up on that list.

One of the landmark symptoms of endometriosis is serious menstrual pain - known as dysmenorrhea. Nettle™ is not intended to cure any conditions. However, while Nettle™ does not treat endometriosis, it is intended to help manage one of its most debilitating symptoms - that of menstrual pain, making the life of women with endometriosis easier. So far, women with endometriosis are common among our early testers, and say their lives are much better once they have an option for drug-free pain management, which also helps them with mood management during PMS.

If you do have endometriosis and use Nettle™ to manage your mood or pain symptoms, please make sure you start running sessions daily, a few days prior to the expected start of your symptoms, up to 20 days in a row. While you could use Nettle™ more, most people will notice a difference within this period of time, and additional sessions are not necessary, but maintaining a regular schedule (use Nettle™ again after taking a 5-10 day break).

If you feel cognitive symptoms of PMS that seem to be cyclical, such as low mood, mood changes, irritability, anger, and cravings - Nettle™ may be for you.

Sometimes, women on hormonal contraception or otherwise experiencing amenorrhea - missing periods - may still get cognitive symptoms associated with hormonal fluctuations, even though it may be more challenging to initially notice that these symptoms were triggered by hormonal fluctuations. We intend for Nettle™ to help manage those cyclical symptoms.

Women’s health problems have been misunderstood and ignored for too long. We know how hard it is to receive appropriate diagnoses in this area, and we’re working to make Nettle™ available to everyone who needs it.

Nettle™ is available for the reduction of pain, improvement of mood and functionality associated with menstruation and PMS, and does not require a formal clinical diagnosis. If you feel cognitive symptoms of PMS on the days leading up to your period, such as low mood, mood changes, irritability, anger, and cravings; and/or you feel menstrual pain that impacts your wellbeing during menstruation - Nettle™ may be for you. We also encourage you to share our doctor guide with your GP to evaluate if Nettle™ is the right solution for you.

Yes. However, Nettle™ needs to be applied for 20 minute-sessions daily during the late luteal phase, which makes it a high-intensity in-clinic treatment, so we recommend using Nettle™ in at-home settings for convenience and flexibility.

We have not yet completed trials specifically including only women with a diagnosis of PMDD and/or PCOS. However, about 40% of women recruited for their PMS symptoms in our WIND clinical trial met the clinical diagnostic criteria for PMDD, as determined by post-hoc analyses. Our completed clinical trials did not collect data on existing PCOS diagnoses. Our ongoing clinical trials for these specific conditions should come out in the next year, and you can find individual users' reviews here before then.

Yes. 47.1% of participants in our clinical trials self-identified as women of colour, 67.6% of them had wavy, curly or coiled hair, and trial participants had a BMI range from 19 to 29. 

Though Nettle™ has been verified to offer promising benefits in managing mood symptoms associated with premenstrual syndrome (PMS), its efficacy for the treatment of major depressive disorder (MDD) specifically has not been tested. However, large-scale meta-reviews have determined that there is level A (definitely effective) evidence for the use of tDCS targeting the dorsolateral prefrontal cortex in the treatment of MDD, and more research continues to emerge. The use of Nettle™ for MDD treatment should be technically similar to the use of any other tDCS equipment targeting the DLPFC, but would be considered to be “off-label” in the context of Nettle™'s intended use.

Though Nettle™ has been verified to offer promising benefits in managing menstruation-related pain through its transcranial direct current stimulation (tDCS) technology, its efficacy for chronic pain that is not of menstrual origin has not been clinically validated.

Large-scale meta-reviews have determined that there is level B (probably effective) evidence for the use of tDCS targeting the motor cortex in the treatment of neuropathic pain, migraines, fibromyalgia and stroke rehabilitation, and more research continues to emerge. However, chronic pain can arise from various causes and might require different interventions targeting the specific mechanisms involved in each type of pain. At the moment, recommending Nettle™ for chronic pain unrelated to menstrual conditions is not yet supported by the current scope of clinical evidence. 

Though Nettle™ has been verified to offer promising benefits in managing mood symptoms associated with premenstrual syndrome (PMS), its specific efficacy in treating premenstrual dysphoric disorder (PMDD) has not been clinically validated. It is worth noting, however, that PMDD is severely under-diagnosed. In Samphire’s clinical trials focused on PMS, post-hoc analyses showed that 38% of women in the sample matched the clinical diagnostic criteria for PMDD even though patients believed to be experiencing only PMS symptoms.

Since Nettle™'s clinical validation pertains specifically to managing mood symptoms associated with PMS, it may not be appropriate to recommend it as a primary treatment for PMDD. PMDD often requires a comprehensive approach, including psychotherapy, medication, and lifestyle changes. Given that Nettle™ is not known to have any interactions with other treatments, it may be a suitable option to incorporate into a holistic PMDD treatment plan. Before recommending Nettle™ or any other treatment to patients with PMDD, it's essential to consider their individual symptoms, medical history, and preferences. Consulting with a healthcare professional who specialises in PMDD management would be prudent to ensure the most appropriate and effective treatment plan for your patients.

From a technical and scientific standpoint, Nettle™ stimulates two regions of the brain - the DLPFC, associated with mood improvement, and the motor cortex, associated with pain relief, - while Flow Neuroscience’s device only stimulates the DLPFC, associated with mood improvement. 

From an intended use perspective, Flow Neuroscience’s device is approved for the treatment of Major Depressive Disorder (MDD) only. Nettle™ is approved to assist in the management of pain relating to menstruation and mood symptoms relating to premenstrual syndrome.

Therefore, if your patients are interested in managing mood and pain symptoms, associated with menstruation, Nettle is a better fit. If your patients are interested in managing MDD only, Flow Neuroscience’s device is a better fit.