Because your pigment genetics are set to freckle: ephelides are genetically determined but sunlight-induced - UV triggers melanocytes to dump pigment in scattered patches instead of an even tan, and MedlinePlus names MC1R (the red-hair gene) as the major freckle gene.
Sun spots (solar lentigines) are the other kind - cumulative photodamage that does not fade in winter. Freckles are harmless, but they mark sun-sensitive skin: the freckle-prone phenotype burns easier and carries higher skin-cancer risk. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Why do I freckle in the sun?
Because your pigment system is genetically set to freckle, and sunlight is the trigger that flips it on. The dermatology review of freckling separates the two kinds: ephelides - the classic sun freckle - are largely genetically determined but induced by sunlight: UV hits, and your melanocytes respond by dumping pigment into the top skin layer in scattered patches instead of an even tan. Solar lentigines (sun spots) are different - those come from accumulated photodamage over years and do not fade in winter the way ephelides do. The genetics: MedlinePlus identifies MC1R as the major freckle gene - the same red-hair gene; certain variants produce patchier, less protective pheomelanin, which is why freckling clusters with red or blonde hair and fair skin. The honest health read: freckles themselves are harmless, but they are a reliable marker of sun-sensitive skin - the freckle-prone phenotype burns easier and carries higher skin-cancer risk, so they are your skin posting its own warning label. Protection is the same as for any fair skin: daily SPF, and watch any spot that changes, darkens asymmetrically, or looks unlike the others.