Common systemic causes

• liver disease - symptom of biliary obstruction, may be the presenting feature in primary biliary cirrhosis or drug-induced cirrhosis
  
  
• chronic renal failure
  
  
• thyroid disease - hypo- or hyperthyroidism
  
  
• carcinomatosis (especially bronchial)
  
  
• iron deficiency
  
  
• diabetes mellitus
  
  
• parasites:
  • onchocerciasis
  • schistosomiasis
    
    
• lymphoma - may be the presenting feature in Hodgkin's disease
  
  
• pregnancy (pruritus gravidarum) - some women develop pruritus during pregnancy, usually in the later stages but possibly, as early as the third month. Often attributed to oestrogens
  
  
• pre-eruptive herpes zoster

Reference:

• Sheretz EF et al (1992). Skin reactions to systemic disease. Medicine International, 102:4278-81.