What Causes Freckles, Moles, and Birthmarks

Freckles form when clusters of melanocytes overproduce pigment after sunlight exposure.
Moles are small groups of pigment cells that grew together instead of spreading evenly.
Birthmarks often appear from blood vessel or pigment irregularities during development.
Freckles fade in winter but darken in summer — they’re sunlight’s calling card.
Moles can appear throughout life and sometimes change with hormones or age.
Some birthmarks, like port-wine stains, stem from tiny capillary clusters under the skin.
Genetics play a major role in whether you freckle or tan.
Most moles are harmless, but irregular borders or colors deserve medical checks.
New freckles are signs of UV exposure — the skin’s memory of the sun.
Every mark on your skin is part of your personal biological map.