The ABCDE Rule — how to self-assess a mole

Most moles on our bodies are completely harmless. The problem arises when a mole starts to change — and that is exactly where the ABCDE rule comes in. It is a simple method that lets anyone make a preliminary assessment of whether a mole needs a dermatologist's attention.

A Asymmetry

A healthy mole is usually symmetrical — if you divided it in half, both halves would look similar. If one half of a mole clearly differs from the other (in shape, colour, or thickness), that is a signal worth watching.

In J-Skin you can use the symmetry axis tool in the Analysis screen to overlay a dividing line on your mole photo and easily check whether both sides match.

B Border

Benign moles have smooth, well-defined borders. Borders that are concerning include:

• Irregular — jagged or wavy edges
• Blurred — the edge of the mole blends gradually into the surrounding skin
• Notched — deep indentations cutting into the mole

J-Skin uses an 8-sector border clock in the ABCDE module — you can mark which sectors have an abnormal border.

C Colour

A typical mole has a uniform colour — different shades of brown are normal, but they should be evenly distributed. Concerning signs include:

• Multiple clearly distinct colours (dark brown, light brown, black, red, white, blue)
• A sudden colour change in part of the mole
• The appearance of a new shade

The colour sampling tool in J-Skin lets you tap different spots on the mole photo and see how many colour shades are present.

D Diameter

The classic threshold is 6 mm — roughly the size of a pencil eraser. Moles larger than 6 mm should be watched carefully. However:

Many melanomas are smaller than 6 mm at the time of detection. Diameter is one criterion, not the only one.

J-Skin automatically measures moles in millimetres using coin calibration — simply place a coin next to the mole when taking a photo and the app will calculate the actual size.

E Evolution

This is the most important criterion. Any change in a mole's appearance — shape, colour, size, texture — or the appearance of new symptoms (itching, bleeding, crusting) is a reason to visit a dermatologist.

That is exactly why J-Skin was created: regularly photographing moles and comparing photos over time allows you to catch changes that are hard to notice with the naked eye.

When should you see a dermatologist immediately?

Do not wait for your next monitoring session if you notice:

• A mole that bleeds without any injury
• A mole that itches or hurts
• A new mole that is growing rapidly
• A mole that looks completely different from all the others on your body (the so-called ugly duckling sign)
• A dark streak under a fingernail or toenail

How does J-Skin help with the ABCDE rule?

The app offers a complete set of tools for each criterion:

• A — Symmetry axes and mirror reflection in the Analysis screen
• B — 8-sector border clock in the ABCDE module
• C — Colour sampling and posterisation in the Analysis screen
• D — Automatic measurement in mm with calibration using 7 coins
• E — Photo history, 4 comparison modes, diameter chart, timelapse