Differential Diagnosis for Itching

• Single most likely diagnosis
  • Dry skin (xerosis): This is a common condition that can cause itching due to the lack of moisture in the skin, especially during dry weather or in older adults.
• Other Likely diagnoses
  • Eczema (atopic dermatitis): A chronic skin condition characterized by itchy, inflamed skin, often associated with allergies or asthma.
  • Allergic reactions: Itching can be a symptom of an allergic reaction to substances like insect bites, certain foods, or medications.
  • Psoriasis: An autoimmune condition that speeds up the life cycle of skin cells, causing cells to build up rapidly on the surface of the skin, leading to itching and other symptoms.
  • Scabies: A skin infestation caused by the itch mite, leading to severe itching, especially at night.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignancy (e.g., lymphoma): Some types of cancer, such as lymphoma or leukemia, can cause itching due to the release of substances that stimulate nerve endings.
  • Liver disease: Certain liver conditions, like primary biliary cirrhosis, can cause itching due to the buildup of bile salts in the skin.
  • Kidney disease: Itching can be a symptom of kidney failure, possibly due to the accumulation of toxins in the body.
  • Thyroid disorders: Both hyperthyroidism and hypothyroidism can cause itching, although the exact mechanism is not fully understood.
• Rare diagnoses
  • Neurological disorders (e.g., multiple sclerosis, neuropathy): Certain neurological conditions can cause itching due to damage to nerve fibers.
  • Insect bites or stings from rare species: Some insects, like the kissing bug, can cause severe itching and potentially life-threatening reactions.
  • Aquagenic pruritus: A rare condition where water contact causes itching without any visible skin lesions.
  • Cholestasis of pregnancy: A condition that occurs in some pregnant women, characterized by severe itching due to bile flow obstruction.