Pruritus, the medical term for itching, describes an irritating sensation on the skin that prompts a desire to scratch. While common factors like dry skin, allergies, or insect bites can cause itching, it can also signal various underlying health conditions, including some cancers. It is important to recognize that itching is not a frequent or definitive sign of cancer, and most itching experiences are not related to a cancer diagnosis.
How Cancer Can Cause Itching
Cancer can lead to itching through several distinct physiological mechanisms.
Tumors positioned on or near the skin might directly irritate nerve endings, causing a localized itching sensation. This direct irritation can also arise from the tumor’s growth affecting skin structures.
Beyond direct irritation, cancer can trigger systemic effects that result in widespread itching. Cancer cells or the body’s immune response to them can release chemicals, such as cytokines and histamines, into the bloodstream. These substances can irritate nerve endings in the skin, leading to widespread itching.
Organ dysfunction caused by cancer also contributes to itching. For example, cancers affecting the liver or bile ducts can impede bile flow, leading to a buildup of bilirubin and bile salts in the blood and skin. These accumulated chemicals stimulate nerve fibers, causing intense itching. Similarly, kidney dysfunction due to cancer can result in a buildup of waste products that irritate the skin.
Blood cancers can also induce itching through various systemic reactions. While the exact reasons are not fully understood, it is thought that abnormal blood cells or substances released by them can irritate nerve endings in the skin.
Cancers Associated with Itching
Itching is a more commonly reported symptom in certain types of cancer, often linked to the mechanisms described previously.
Lymphomas, particularly Hodgkin lymphoma and some non-Hodgkin lymphomas, frequently cause itching. This occurs because the immune system releases chemicals like cytokines in response to cancer cells, irritating skin nerve endings.
Leukemias, including acute lymphocytic, chronic lymphocytic, chronic myeloid, and polycythemia vera, can also be associated with itching. This may be due to substances released by blood cells or the overproduction of immune cells.
Cancers that affect the liver or bile ducts, such as liver cancer, pancreatic cancer, and bile duct cancer, often lead to itching. This is primarily caused by the obstruction of bile flow, resulting in the accumulation of bile salts and bilirubin under the skin.
Skin cancers, including basal cell carcinoma, squamous cell carcinoma, and melanoma, can cause itching, especially as the lesion grows. Itching in these cases often stems from direct irritation of nerve endings by the tumor or an inflammatory response. While less common than other skin cancer symptoms, an itchy mole can be a sign of melanoma.
When to Seek Medical Advice for Itching
Persistent itching without a clear explanation warrants medical evaluation, especially if it lacks an obvious cause like dry skin, allergies, or insect bites, or significantly disrupts daily activities.
Itching accompanied by other general symptoms can be a signal to seek professional advice. These “red flag” symptoms include unexplained weight loss, persistent fatigue, fevers, or drenching night sweats. Enlarged lymph nodes or noticeable changes in skin appearance, such as new growths or changes in existing moles, also indicate the need for medical attention.
Generalized itching can be more concerning. While most itching is benign, persistent, unexplained, or widespread itching, especially when combined with other concerning symptoms, should prompt a discussion with a doctor.