Dry Skin (Xerosis): This is often the most common cause of generalized pruritus without a rash, especially in elderly patients or during dry weather conditions. It can be exacerbated by excessive bathing, harsh soaps, or low humidity.

Atopic Dermatitis: Although it typically presents with a rash, atopic dermatitis can sometimes cause pruritus without visible skin changes, especially in the early stages or in patients with darker skin tones.
Psoriasis: Similar to atopic dermatitis, psoriasis can occasionally present with pruritus before the appearance of characteristic skin lesions.
Uremic Pruritus: Patients with chronic kidney disease or those undergoing dialysis may experience generalized pruritus due to the buildup of uremic toxins.
Hepatobiliary Disease: Certain liver conditions, such as primary biliary cirrhosis, can cause pruritus without a rash, often due to the accumulation of bile salts in the skin.
Hypothyroidism: Some patients with hypothyroidism may experience generalized pruritus, although the exact mechanism is not fully understood.
Iron Deficiency Anemia: Iron deficiency has been associated with pruritus, possibly due to the role of iron in neurotransmitter synthesis and skin health.

Lymphoma: Certain types of lymphoma, such as Hodgkin's lymphoma, can present with generalized pruritus as an initial symptom, often without a rash.
Leukemia: Similar to lymphoma, some forms of leukemia can cause pruritus due to the release of histamine or other chemical mediators from leukemic cells.
Thyroid Cancer: Rarely, thyroid cancer can cause generalized pruritus, possibly due to the production of pruritogenic substances by the tumor.
Paraneoplastic Syndromes: These are rare disorders that occur in association with cancer, where the cancer itself does not directly cause the symptoms but triggers an immune response that does.

Polycythemia Vera: A myeloproliferative disorder that can cause pruritus, typically after hot showers, due to the release of histamine from basophils.
Neurological Disorders: Certain neurological conditions, such as multiple sclerosis, peripheral neuropathy, or neuropsychiatric disorders, can cause pruritus without a rash, often due to central or peripheral nervous system dysfunction.
Cholestasis of Pregnancy: This condition occurs in pregnant women and is characterized by severe pruritus, usually without a rash, due to the impairment of bile flow.
Aquagenic Pruritus: A rare condition where water contact induces pruritus without any visible skin changes, possibly related to the release of histamine or other mediators.