Case study

Skin Cycle

A private skin diary that gives skincare tips for each phase of the menstrual cycle — built so its health claims can be traced to sources.

The problem

Skincare advice online is full of brand pushing, myths and "toxic" scare scores. Advice about skin and the menstrual cycle is often stated with more confidence than the research supports.

My role

Sonali Krishnani on LinkedIn · GitHub profile · Zenodo DOI

• Came up with the idea: skin first, with the cycle as context — not a period tracker.
• Set the rules: ingredient types, not brands; no "toxic" scores; no scraped reviews; a caution on every remedy.
• Led three rounds of fact-checking and decided what to cut and keep.
• Built it with Claude Code, an AI coding assistant, which wrote the code and ran the research agents.

How the advice was checked

Every claim was treated as wrong until an opened source backed it: AAD, NHS, HSE, DermNet, FDA or a published study. The findings are written up in the AI-assisted rapid review.

• Cut: honey (in a trial, adding it to soap did no better than soap alone) and aloe vera (weak evidence, can cause rashes).
• Corrected: an incomplete pregnancy note, an under-urgent warning sign, a mislabelled source.
• Moved to myths: the "ovulation glow".
• Result: 67 sources, every tip linked to at least one, and automated tests that fail if a tip loses its source or a remedy its caution.

Key decisions

• Private by default. No account, no server — data stays on the device.
• Honest about evidence. The app says research on skin across the cycle is thin, and shows a pattern only when your own ratings support one.
• Your routine. Pick suggested steps or type your own.
• A demo for visitors. A guided walk-through of a sample diary, so anyone can see it without setting it up.
• Accessible. Large tap targets, readable contrast, works on a phone.

Limits

• Not yet reviewed by a pharmacist or dermatologist — the checks were done by AI agents against published sources.
• General skincare information, not medical advice or contraception.
• Data lives in one browser; clearing site data erases it.

Built with

React, TypeScript, Vite and Tailwind. Tested with automated checks on the cycle maths and the content.