Pruritus is a disagreable sensation that provokes a desire to scratch .Pruritus is an important skin symptom and occurs in dermatological diseases such as atopic eczema ,many cases can be attributed to dry skin , many other causes ,scabies ,dermatitis herpetiformis ,pruritus vulvae or ani ,insect bites ,pediculosis ,contact dermatitis ,drug reactions
,urticarial eruptions of pregnancy ,psoraisis,lichen planus ,lichen simplex chronicus ,exfoliative dermatitis .
Persistant pruritus not explained by cuteanous disease should prompt a staged workup for systemic causes ,the most common cause of pruritus associated with systemic disease is uremia in conjunction with hemodialysis In primary biliary cirrhosis the disease starts insidously most frequently without jaundice ,jaundice may never develop but in the majority appears within 6 months to 2 years of the onset of pruritus ,. Causes of generalized pruritus :
-Obstructive liver disease -Hematological : Iron defeciency anemia , polycythemia -Endocrine : Hyperthyroidism, Hypothyroidism ,Diabetes mellitus . Chronic renal failure - Malignancy : Internal malignancies , lymphoma Drugs: Morphine . Other :
Pregnancy -senelity .Both pruritus of uremia and the pruritus of liver disease may be helped by phototherapy with ultraviolet B or PUVA.Naltrexene and nalmefene have been shown to releive the pruritus of liver disease . Naltexone is not effective in pruritus associated with renal failure but gabapentin may be effective