MadSci Network: Anatomy
Query:

Re: why do my hand freckles disappear in winter while my arm freckles do not?

Date: Tue Jan 16 14:58:51 2001
Posted By: Brian Edelson, MD/PhD Student
Area of science: Anatomy
ID: 973219227.An
Message:

Your question is good.

I'm not certain of the answer, but I think there is a distinction to be made 
between freckles, which come and go based on sun exposure, and moles, which 
are basically darker, permanent skin marks (also called beauty marks).

Both are dark due to the production of the pigment melanin, which as you 
said is made by melanocytes.  There are melanocytes spread evenly throughout 
your skin, which give you your background skin color.  In some spots (moles) 
there is a bunch of melanocytes together, which continuously are making 
melanin, giving you the mole.  For the case of freckles, melanocytes in a 
little area started temporarily making more melanin due to sun exposure, but 
stop when the sun exposure stops (i.e. in the winter).  The melanin then 
fades away from the freckles as the skin cells naturally turnover and get 
replaced by new ones, leaving you without a freckle in this spot (until next 
summer!).

Moles have the potential for changing over the course of one's lifetime.  
Often the change is not dangerous, but sometimes the mole changes into a 
cancer called melanoma.  The chance of melanoma increases if you spend lots 
of time in strong sun without any sunscreen.  If a mole changes in shape, 
color, or becomes raised, you should see a doctor about whether it may need 
removal.

Hope this helps,

BRIAN E.



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