Melanoma Warning Signs: What to Look For and When to Act
The ABCDE rule, the ugly-duckling sign, and the specific mole changes that warrant a same-week dermatologist visit.
Melanoma is the deadliest form of skin cancer, but it is also one of the most curable when caught early. Five-year survival is above 99 percent for localized disease and drops sharply once it spreads. Almost every melanoma is visible on the skin before it becomes dangerous, which is why self-exams and dermatologist visits matter so much.
This guide covers what dermatologists actually look for, the mole changes that should move you to the top of the schedule, and the ones that don't.
The ABCDE rule in practice
Asymmetry, Border irregularity, Color variation, Diameter over 6mm, and Evolution. Any one is worth showing a dermatologist. Evolution — change over weeks or months — is the strongest single signal.
Take phone photos of any mole you're watching. Compare monthly. The camera catches drift that memory misses.
The ugly duckling sign
Most people have their own mole 'pattern.' A lesion that looks meaningfully different from your other moles — darker, larger, or a different shape — is worth checking, even if it doesn't hit all five ABCDE criteria.
Melanoma on darker skin
Acral melanoma appears on palms, soles, under nails, and mucous membranes, and disproportionately affects Fitzpatrick V and VI. A dark streak under a nail that wasn't there last year is the classic presentation. Reggae legend Bob Marley died of acral melanoma diagnosed too late.
When to book same-week
A mole that bleeds, itches, or crusts without trauma
A rapidly growing pink or red bump
A new pigmented streak under a fingernail or toenail
Any mole that looks obviously different from your others
Key takeaways
ABCDE plus the ugly-duckling rule catch most melanomas.
How to read this Melanoma Warning Signs: What to Look For and When to Act page
The UV index is a measure of erythemal (skin-reddening) irradiance, where each whole point equals 25 mW/m² of UV energy reaching the surface. That is why burn-time estimates fall roughly by half when the index doubles.
UV strength on this page follows solar elevation, ozone thickness, cloud cover, altitude, and surface reflection. Snow can bounce back most of the UV that hits it, water and sand far less, but all of them add to the dose skin receives.
Plan outdoor blocks around the peak UV window, usually between 10am and 4pm local time. Shade, UPF fabric, a wide-brim hat, and UV-blocking sunglasses reduce dose more reliably than sunscreen alone.
Cloud cover is not protection. Thin or broken cloud can still pass most incoming UV, and light cloud edges can briefly scatter more UV toward the ground than a clear sky.
Cumulative dose drives photoaging and long-term skin damage more than any single day. Small daily exposures on commutes, walks, and driving add up across a season.
UV scale reference
The WHO scale groups UV 1-2 as low, 3-5 as moderate, 6-7 as high, 8-10 as very high, and 11 or above as extreme. Protection is recommended from UV 3 upward, and shade during the middle of the day becomes the priority from UV 8 upward.
A practical routine at moderate-to-high UV is roughly one ounce of broad-spectrum sunscreen for full-body coverage, applied 15 minutes before going out, then reapplied on schedule. Clothing, hats, and shade carry the rest of the load, especially for children and anyone with a history of easy burning.
Keep exploring DermUV
These pages give more depth around melanoma warning signs: what to look for and when to act, from UV-scale reference material to calculators and city forecasts.