World Library  
Flag as Inappropriate
Email this Article

Freckle

Article Id: WHEBN0000058180
Reproduction Date:

Title: Freckle  
Author: World Heritage Encyclopedia
Language: English
Subject: Vitiligo, Postinflammatory hyperpigmentation, Kangri cancer, Pityriasis rubra pilaris, Sunburn
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Freckle

Freckle
Classification and external resources
Slight facial freckles on a child.
ICD-10 L81.2
ICD-9 709.09
OMIM 266300
eMedicine article/1119293
MeSH D008548

Freckles are clusters of concentrated melanin which are most often visible on people with a fair complexion. A freckle is also called an ephelis. Freckles do not have an increased number of melanin producing cells (melanocytes), but instead have cells that overproduce melanin granules changing the coloration of the skin. This also causes the different skin tones among humans, but contrasts to lentigines and moles.[1]

black and white photos show contrast in freckles

Biology

Freckles can be found on anyone no matter their genetic background; however, the number of freckles is genetic and is related to the presence of the melanocortin-1 receptor MC1R gene variant.[2] The formation of freckles is triggered by exposure to sunlight. The exposure to UV-B radiation activates melanocytes to increase melanin production, which can cause freckles to become darker and more visible.

Freckles are predominantly found on the face, although they may appear on any skin exposed to the sun, such as arms or shoulders. Heavily distributed concentrations of melanin may cause freckles to multiply and cover an entire area of skin, such as the face. Freckles are rare on infants, and more commonly found on children before puberty. Upon exposure to the sun, freckles will reappear if they have been altered with creams or lasers and not protected from the sun, but do fade with age in some cases.

Freckles are not a skin disorder, but people with freckles generally have a lower concentration of photo protective melanin, and are therefore more susceptible to the harmful effects of UV radiation. It is suggested that people whose skin tends to freckle should avoid overexposure to sun and use sunscreen.[3][4]

Types of freckles

Ephelides describes a freckle which is flat and light brown or red and fades with reduction of sun exposure. Ephelides are more common in those with light complexions, although they are found on people with a variety of skin tones. The regular use of sunblock can inhibit their development.

Liver spots (also known as sun spots and lentigines) look like large freckles, but they form after years of exposure to the sun. Liver spots are more common in older people.

See also

References

Citations

  1. ^ Robbins and Cotran Pathologic Basis of Disease Elsevier. 2005. Page 1232. ISBN 0-8089-2302-1 .
  2. ^ Online 'Mendelian Inheritance in Man' (OMIM) Skin/Hair/Eye Pigmentation, variation in, 2; SHEP2 -266300
  3. ^ Hanson Kerry M.; Gratton Enrico; Bardeen Christopher J. (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin". Free Radical Biology and Medicine 41 (8): 1205–12.  
  4. ^ Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health 82 (4): 614–5.  

Bibliography

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.