Effective date: 28 April 2026
Last updated: 22 July 2026
SIS ("we", "our", or "us") is a pattern-tracking and summary tool designed to help individuals record symptoms, appointments, and health-related information in a calm, non-diagnostic way.
Your privacy is foundational to how SIS is built. This policy explains, plainly and fully, how your information is handled when you use SIS.
SIS allows you to enter personal health-related information, including:
This information is entered voluntarily by you and is stored only on your device, in your browser's local storage, under the keys womens-health-pattern-app, sis-diary-entries, and womens-health-documents.
We do not transmit, copy, back up, or have any access to this information. (The one exception is the optional Big Sis feature, which sends only what you choose — see section 6.) If you clear your browser's data, the information is gone — including from us, because we never had it.
SIS uses Plausible Analytics, a privacy-friendly, EU-hosted analytics service designed to be compliant with GDPR, ePrivacy, PECR, and CCPA without requiring a cookie banner.
What Plausible collects:
What Plausible does not do:
Where this analytics is and isn't used: Plausible is enabled on the main SIS app pages so we can understand whether the tool is reaching people and which features are useful. It is disabled on the founder's personal story page (story.html) — that page is a personal account and we don't believe visits to it should be counted, even anonymously.
Plausible's own privacy policy is available at plausible.io/privacy.
If you contact us at hello@bigsis.health, we will see your email address and the contents of your message. We use this only to reply to you. We do not add you to any mailing list, and we do not share your email with anyone.
The hello@bigsis.health address is forwarded to a personal inbox managed by the founder. Email is not encrypted end-to-end — please don't include sensitive medical details in messages to us.
We do not:
The optional Big Sis feature is the one exception: when you use it, de-identified information you choose is sent to an AI provider, acting on your instruction, to generate your reply (see section 6). This is a processing service you actively choose to use — not selling, advertising, or sharing your data for anyone else's purposes, which we never do.
Anything you choose to export from SIS (for example, a summary to share with a clinician) is entirely under your control. Once you export it, it leaves the protection of your device — please handle exports as you would any other personal medical document.
Big Sis is an optional, premium feature. Everything above about your health information staying on your device remains true — Big Sis is the single, deliberate exception, and it only ever operates when you choose to use it.
What it does. Big Sis helps you understand a term from your records, prepare questions for an appointment, or organise your journey into a readable summary. To do this it uses an external artificial-intelligence service — currently Claude, made by Anthropic — to generate a reply.
It is opt-in, twice over. Big Sis does nothing unless you turn it on (a one-time consent) and then confirm each individual send. Nothing is sent automatically or in the background.
What is sent — and what is not. Only the specific information you choose for that request is sent. Before anything leaves your device, personal identifiers — your name, email, phone number and the like — are removed, so what is sent describes your experience, not you. We send the minimum needed for the task, never your whole record, and in a continuing conversation only your new message plus the conversation so far. You see exactly what will be sent, and roughly how much, before you confirm.
How it is sent. Your chosen information travels over an encrypted connection to a relay we operate (at ai.bigsis.health) whose only job is to pass the request to the AI provider and return the reply. It stores nothing, keeps no database, and does not log your health content.
The AI provider. The provider (currently Anthropic) processes your request to generate the reply. Under their commercial API terms they do not use the data to train their models and do not retain it after responding. Because what we send is de-identified, it does not identify you.
International transfer. The provider may process your request outside the UK/EU (for example, in the United States). This applies only to the de-identified information you choose to send, and is governed by the provider's data-processing terms and appropriate safeguards.
It still never diagnoses. Big Sis will not tell you what condition you have or interpret your results — it helps you understand and prepare, and routes decisions back to your healthcare team. It is not a medical device.
Your control. You can choose not to use Big Sis at all, use it for only some things, or stop at any time. A conversation is held only in memory while it is open, and is not saved anywhere once you close it.
SIS's long-term mission includes the possibility of feeding anonymous, aggregated patterns — never personal information — back into clinical and research systems, so that the experience of being dismissed becomes harder to repeat.
This is a future feature, not a current one. If and when it is built, it will:
Until then, other than the optional Big Sis feature described in section 6, none of your data leaves your device.
SIS is not a medical device. It does not diagnose, treat, monitor, or make clinical decisions. It is a personal record-keeping and pattern-noticing tool. SIS does not provide medical advice, diagnosis, or treatment, and is not a substitute for advice from a qualified healthcare professional. Always consult your doctor about any medical concerns. Big Sis, the optional AI companion, likewise does not diagnose or give medical advice; it helps you understand and prepare, and points decisions back to your healthcare team.
Because your information is stored only on your device, the security of that information depends on the security of your device and browser. We recommend:
SIS itself is delivered over HTTPS and does not transmit your health information anywhere — except where you actively use Big Sis (see section 6), which sends only the de-identified information you choose, over an encrypted connection.
Because we don't hold your personal health data, most data-protection rights (access, correction, deletion, portability) are exercised directly by you on your own device — your data is yours, immediately and completely.
For the limited information we do process (analytics and any email correspondence), and for the de-identified information you choose to send when you use Big Sis, under EU GDPR, UK GDPR, and equivalent laws in other regions, you have the right to:
To exercise any of these rights, email hello@bigsis.health.
SIS is available globally. Plausible Analytics is hosted in the European Union (Germany). Email sent to hello@bigsis.health is forwarded to an inbox managed by the founder in Cyprus. Because your health data never leaves your device, there are no international transfers of your health information — with one exception: if you use the optional Big Sis feature, the de-identified information you choose may be processed by an AI provider outside the UK/EU (see section 6).
SIS is intended for adults. It is not directed at children. Different countries set the minimum age for digital consent differently (commonly between 13 and 16). If you are under the age of digital consent in your country, please use SIS only with the involvement of a parent or guardian. If you believe a child has used SIS on a device you control and you wish to remove the data, clearing the browser's storage for the SIS site will delete it.
If we make material changes to this policy — for example, adding a new feature that involves processing data differently — we will update this page and revise the "Last updated" date at the top. For significant changes, we will surface a notice in the app itself.
For any privacy questions, requests, or concerns, please email:
SIS is built on the belief that your story belongs to you. This policy is the practical expression of that belief.