With or without a rash, itchiness is the most frequently reported symptom in all of dermatology. Even when there is no rash, the possible reasons for itchiness, or pruritus, are numerous and include various illnesses and even several normal conditions and responses. These causes also tend to overlap, depending on how you look at things. For example, plain old dry skin can cause itchiness, but so can many different systemic illnesses that cause dry skin.
Dry skin is the most common reason for itchiness without a rash. This is especially true in people over 65 years of age. Itchiness without an apparent cause is also more common among older individuals.
Exposures and Reactions
Allergens and irritants can produce itchiness with or without a rash, and sometimes itchiness can precede the development of a rash. Irritants such as a new soap, or a new perfume or cologne may be to blame, and irritants often lead to a cycle of dry skin and itchiness. Normal processes such as pregnancy may be associated with itching, as the skin over the expanding abdomen stretches. In addition, pregnant women occasionally develop a liver problem called cholestasis that's associated with itching. A very rare type of itchiness, termed aquagenic pruritus, is associated with exposure to water of any temperature, alone. Sometimes an unexplained case of itchiness goes away and never surfaces again, while other times, it continues and eventually leads to the diagnosis of an underlying process or systemic disease.
Compounds in the Blood
Certain illnesses are associated with changes in blood chemistry, and these compounds are thought to be involved in causing itchiness. How and why certain compounds promote itchiness is still not completely understood. Urea is a compound that is usually filtered out into the urine by the kidneys. When people have problems with both kidneys not functioning well, or renal failure, the excessive urea is associated with itchiness. When some one has a blockage of the bile system in the liver, or cholestasis, itch is a common symptom. Itch occurs in 80 to 100 percent of patients with blocked bile flow and yellow jaundice of the skin and eyes. Deficiencies can also result in itchiness: iron deficiency, with our without anemia can produce generalized itchiness. The excess of hemoglobin and red blood cells seen in a condition called polycythemia vera is also a cause of itchiness – one that may seem at first to be due to exposure to water.
Drugs and Psychological Causes
Itching is a common side effect of morphine, oxycodone and other opioids, and many forms of illicit drug use are also associated with itchiness. What is more, there is a psychological component to itch, and sometimes it can be significant.
Hormones, Infections and Malignancies
Disorders of the thyroid gland – excess thyroid hormone, and less commonly insufficient thyroid hormone levels – are associated with itchiness. HIV and hepatitis C virus are among the infections linked to generalized itchiness as a symptom. Lymphomas – especially Hodgkin’s lymphoma – are known for itchiness as a potential symptom. Solid tumors such as lung cancer, colon cancer, brain cancer and breast cancer can also cause itchiness.
Reviewed by: Tom Iarocci, M.D.