None of us find itching at one specific spot on the body to be unusual even if it occurs for no clearly identifiable reason. Often this is a transient itch and resolves almost immediately. In some skin diseases this itching can be persistent or recurrent for long periods but it is usually isolated to the diseased area. However, there are times when itching may occur all over the body and persist despite the lack of a skin rash.
What is generalized pruritus?
Generalized pruritus is the medical term for itching throughout the body. Localized pruritus refers to itching isolated to specific areas on the body. Most of us simply refer to generalized pruritus as itching throughout the body or itching all over the body. It is a symptom of several different types of diseases and not only of skin diseases. Sometimes the exact cause is unknown.
WARNING: Itching all over the body that arises suddenly and is accompanied by symptoms like an itchy throat, swelling of the body or difficulty breathing requires immediate medical attention. Any delays could allow thc ondition to rapidly progress and even lead to fatal complications. Always speak to a doctor.
Reasons for Itching
Itching is due to the stimulation of certain types of receptors present in the skin. These receptors, also referred to as the itch receptors, are stimulated by injury and pressure on the skin surface. It can also be stimulated by certain substances. Histamine is one such substance. It is produced and stored in certain types of immune cells and released in large quantities under certain conditions. These substances are endogenous meaning it is produced in the body.
Several exogenous substances can also trigger a reaction. This is mainly when these substances come into contact with the skin and either irritate it or trigger a skin allergic reactions. Inhaled and ingested substances may also be the cause of generalized pruritus. Some cause an immediate reaction upon exposure while others may have a delayed response and it can be confusing to identify the causative substance.
Causes of Itching All Over the Body
Generalized pruritus due to a skin disease may occur if the skin disease affects most of the body surface. This is not common for most skin diseases and therefore it usually presents with localized pruritus. The various dermatologic (skin disease) causes of pruritus has been discussed in greater detail in itchy rash. These conditions either arise in the skin or primarily affect the skin.
However, there are many non-dermatologic causes of of generalized pruritus. These are conditions that are not primarily involving or originating from the skin although there may be some skin symptoms. It includes a range of conditions such as allergies, hormonal problems, liver conditions, kidney disorders and certain blood diseases. Itching can also be psychogenic in nature and may be a symptom of certain mental health conditions.
An allergy is a condition where the immune system is abnormally triggered by some harmless substances. In other words the immune system is hypersensitive and incorrectly identifies the harmless substance (allergen) as a potential danger. Sometimes the allergic reaction may be localized, as is seen in allergic contact dermatitis. The reaction is limited to the area where the allergen makes contact with the skin.
However, with systemic allergies the symptoms may be present throughout the body. This can be seen with certain mild and some very serious allergic reactions. In terms of the latter, anaphylaxis is the main concern. It can start with mild symptoms like itching all over the body and irritation in the throat and progress to extensive swelling and dfficulty breathing.
Itching may also occur with kidney problems like chronic kidney failure and in people undergoing hemodialysis. The term for this type of itching is renal pruritus. It is believed to be due to an accumulation of wastes products that would normally be excreted in urine.
The exact substance responsible for the itching has not yet been conclusively identified. Elevated levels of histamine in the bloodstream could be responsible for itching in people with kidney problems. Abnormally high levels of phosphate, calcium and magnesium may possibly play a role in the itching.
Liver and Gallbladder Itching
Generalized pruritus can also occur in the backdrop of liver and/or gallbladder disease. It occurs in these conditions when bile is either not formed or obstructed from being passed out of the liver and gallbladder. This is known as cholestatic pruritus and is usually associated with jaundice although the yellowing of the skin may not always accompany the itching.
It was previously thought that the accumulation of bile salts in the body, and subsequent deposition in the skin may be the cause of the itching. However, it appears that multiple factors play a role, including the elevated levels of histamine and a build up of opioids produced within the body.
Itchy skin is seen in certain hormone problems (endocrine disorders). This may occur for various reasons but the exact mechanism is not always understood, as is the case with itching in diabetes mellitus. Itching in hypothyroidism (low thyroid hormone levels) appears to be due to dry skin that commonly occurs as part of the disease. In hyperthyroidism the high thyroid hormone levels appear to trigger certain inflammatory chemicals that then cause the itching.
Itching has also been reported among cancer patients, even when there is no skin dryness or chemotherapy. Some of these malignancies may produce and secrete various substances like hormones. This is known as carcinoid syndrome. It also appears that with certain malignancies such as Hodgkin’s lymphoma the immune system’s response to the cancer causes the immune cells to release large quantities of trigger substances like bradykinin.
- Nutritional deficiencies as is seen with iron deficiency even without anemia.
- Polycythemia vera
- Viral infections like chickenpox and measles.
- Infestations like scabies or body lice.
- Adverse drug reactions.
- Climates like in dry air.
- Sunburn (widespread).
- Anxiety or psychological stress.
- Illicit substances like methamphetamines.
- Skin diseases like psoriasis.
- Autoimmune conditions like systemic lupus erythematosus (SLE).