|MadSci Network: Cell Biology|
Freckles are defined as localized hyperpigmentation and they are due to increased pigment production locally. This is distinct from a local increase in the number of pigment producing cells, the melanocytes. Thus, the melanin doesn't go to one spot, but rather that some of the melanocytes which are distributed throughout the skin make more pigment than others. I don't believe that it is fully understood why this difference in behavior occurs.
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