A Photo Diary for Slow Body Changes — Evidence You Can Show Your Doctor

Moles, hair, skin, a rash that comes and goes: these things change so slowly that by the time you see a doctor, all you can say is “I think it got worse”. Bodylog keeps dated, same-angle photos and short notes on your own phone, so the change is there to see.

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The problem

Health worries are among the most common things people look up — in 2019 Google's then head of health, David Feinberg, said about 7% of Google's daily searches are health-related (reported by Becker's Hospital Review). Yet for slow changes, searching does not help much; what helps is a record. The problem is that nobody keeps one. Photos end up scattered through the camera roll between screenshots and holidays, taken from different distances and in different light, so they cannot really be compared. Many people also do not want pictures of their skin, scalp or body synced to a cloud account. So at the appointment the doctor hears a memory instead of seeing a timeline.

How Bodylog (Symptom Photo Diary) works

• Pick what you want to watch: hair, skin, a mole or spot, a rash, weight, sleep, digestion, pain — or name your own topic, such as “left knee”.
• Tap Today, take the photo and tap Save. The previous photo shows faintly over the camera, so you can line up the same angle and distance every time. Add a level from 0 to 3 and a note if you like.
• Each photo is redrawn on your device and saved as a new, compressed JPEG, which removes the location (GPS) and camera data that phones hide inside pictures.
• Before an appointment, open the topic: the chart shows how your own 0–3 rating has moved, the before/after slider puts any two dates side by side, and the report prints the whole story on one or two pages.

What you get

• The last photo as a guideComparing photos only works if they are taken the same way. Bodylog lays your previous photo over the live camera at adjustable strength, so today's shot matches last week's framing. Photos from your gallery work too, and you can overlay the last one on any entry to check.
• Location and camera data removedA phone photo can carry the GPS position of your home. Bodylog never stores the original file: it redraws the image and keeps only a fresh JPEG with no EXIF, no GPS and no camera model — and it still respects the photo's rotation.
• Before/after slider that stays alignedPick any two dates and drag the divider. Both photos sit in exactly the same frame, even when one is portrait and the other landscape, so the line cuts both images at the same point instead of shifting.
• A report made for a ten-minute appointmentOne tap prints a short summary on A4 or US Letter: your name if you want it, the questions you want to ask, the timeline chart, key photos (or all of them) and every entry with its date, level and note. Photos never split across pages. Save it as a PDF or print it.
• “When to see a doctor now”Bodylog does not interpret anything, so it keeps a short, sourced list of warning signs inside the app — for example a rash that does not fade under a pressed glass, or a mole that changes size, shape or colour — with links to the NHS and MedlinePlus pages they come from.

Private by design

Bodylog has no account and no server. Photos and notes are stored in your browser's storage on your phone and are never uploaded; the only network request the app ever makes is the one-time check of a Pro licence key. With Pro you can add a passcode: notes and every photo are then encrypted on the device with AES-256 (key derived with PBKDF2-SHA256, 200,000 rounds), and after five wrong attempts the app makes you wait before trying again. If you forget that passcode, nobody can recover the data — including us. Bodylog is a record-keeping tool, not a diagnosis: it has no AI and no image analysis, it is not a medical device or an official medical record, and it does not replace a doctor.

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