Milia Workup

Updated: Mar 10, 2017
  • Author: Charles M G Archer, MBBS, MRCP(UK); Chief Editor: William D James, MD  more...
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Laboratory Studies

No investigations are needed for simple milia. The clinical appearance is diagnostic. Investigation of the underlying disease is necessary in persons with secondary milia.



Performing a skin biopsy is necessary only if the diagnosis is in doubt. If milia en plaque is suspected, performing a biopsy is prudent to exclude follicular mucinosis and multiple trichoepitheliomata. In an elderly person with sun-damaged skin, Favre-Racouchot syndrome (nodular elastosis of the skin) needs to be excluded.


Histologic Findings

The histological features are identical to those of epidermoid cysts, but the cysts are much smaller. The milium is usually located in the superficial dermis and has a complete epithelial lining (with a granular cell layer). It contains a variable amount of lamellated keratin. The common primary milia in infants and children are found in the undifferentiated sebaceous hair collar surrounding vellus hair follicles. Milia secondary to blistering are often found in eccrine sweat ducts.