More than most people expect, and less than some services imply.
Photographs work well for: acne, eczema, psoriasis, fungal infections, impetigo, rashes with a clear distribution, and following up something already diagnosed. The pattern, the distribution and the appearance carry most of the diagnostic information.
Photographs are unreliable for:
- Moles. Assessing a pigmented lesion properly needs dermoscopy — a magnified polarised view no phone camera reproduces. A reassuring photo is not a reassuring examination
- Lumps. What matters is how it feels — whether it is fixed, fluctuant, tethered
- Anything needing pressure, palpation or a device — an eardrum, a chest, an abdomen
- Colour-critical judgements, since phone cameras and lighting distort colour considerably
How to take a useful photograph: natural daylight, no flash, one wide shot showing the location on the body and one close-up in focus, and something for scale such as a coin. Take it from a few angles.
Where a photograph is not enough, we will say so and arrange in-person assessment rather than guess.