What is Pruritus?
Causes of generalised itching
Many tumours, particularly those of the Lymph node system release an unknown chemical which causes generalised itching. Sometimes this may be the first symptom of cancer and patients notice a marked improvement when chemotherapy starts. Often patients have a return of the itching if the tumour relapses even before it is detected on a scan. In these cases itching may be associated with weight loss or excess sweating particularly at night. These symptoms are often called by doctors paraneoplastic.
The best treatment for this type of itching is to treat the tumour but see general treatments below.
Liver related – If the flow of bile from the liver to the bowel is interrupted patients become yellow (jaundiced). This is due to a build up of bile in the blood stream which then gets deposited in the skin and whites of the eyes.
Along with bile there is a second chemical called Bile salts – these also get deposited in the skin and cause distressing itching. Liver problems may be associated with pain in the right upper part of the abdomen, feeling nauseated and indigestion.
Your doctor may already know why the flow of bile in your bile duct is impaired but if not several investigations can be performed:-
Blood tests – for bile levels (bilirubin), liver function tests
Liver ultrasound – looking for blockage in the bile duct
CT or MRI or the abdomen – to see if lymph nodes are enlarged near the end of the bile duct or cancer is seen within the liver.
ERCP – If the tests above do not find out the problem a scope can be passed through the mouth into the part of the bowel next to the bile duct. Dye is injected up the duct and an xray taken – this will tell the doctors what type of obstruction you have including non-tumour conditions such as gall stones.
Treatment for liver related pruritis – The most effect way to relieve this itching is to correct the normal flow of bile. If this is caused by tumour at the base of the bile duct. Removal of this tumour may be possible either with surgery, chemotherapy or radiotherapy.
For tumours of the pancreas for example it may be possible for the surgeon to bypass the obstruction by moving the bile duct to another part of the bowel. It is also possible that a plastic stent can be inserted into the bile duct at the time of ERCP (see above) to drain the bile and bile salts.
If physical relief of the obstruction is not possible the level of bile salts in the blood stream can be reduced by taking a medication called Cholestyramine. Also general measures for itching also apply (see below)
Renal related – Renal failure is normally very advanced before it causes itching. This is caused by the urea being deposited in the skin. It is usually long standing and your doctors should be aware of the cause.
Treatment – correct the renal failure or see general measures.
Iron Deficiency Tumours of the urological, gastrointestinal or gynaecological system can bleed. These often present with anaemia (see anaenia related fatigue). It is sometimes possible for the the body to replace the blood but use up the iron stores. This is usually if there has been slow blood loss over a long period of time. This can cause a mild generalised itching and improves when the source of blood loss is corrected and iron medication is given.
Hormone disorders – very rarely thyroid and parathyroid disorders can lead to itching.
Morphine withdrawal – Patients on morphine, or morphine like drugs often experience itching especially if the dose is reduced.
Drug reaction – Virtually any drug can produce a skin rash caused by an allergic reaction to the drug. Some drugs are more likely to cause a rash than others. . The drugs most commonly associated with a drug reaction are antibiotics (peniciilin, cephalosporins, sulphonamides), Hormones (tamoxifen, arimidex, femara, cyperoterone acetate), Anti-gout drugs (allopurinol) and anti-inflammatories (ibobrufen, diclofenac). There are different types of drug reactions
Common drug reaction – A widespread red rash (maculo-papular rash / Morbilliform drug reaction) – This is the most common type of drug reaction. The rash occurs throughout the whole body but particularly the trunk. It is usually very itchy and the reddened areas are and slightly raised & knobbly. It usually resolves within a 1-2 weeks when the drug is stopped.
“Weal’s & Flares”. (Urticaria like reactions) – Red patchy blotches. The skin is raised, sometimes with a pale centre.
Target lesions which are itchy / painful . (Erythema multiforme). This is a rare serious and form of of drug reaction. Target like lesions can form on any part of the body, particularly the hands. Often associated with mouth ulcers and in its most serious form damage to the kidneys. This can be associated with any drug but most likely aspirin like preparations or an antibiotic called sulphonamides.
Blisters & ulcers – (toxic epidermal necrolysis). A severe and rare reaction characterised by widespread blisters which burst to form superficial ulcers. These ulcers the when healing form a scab within 1-2 weeks, which then take another 2-3 weeks to completely heal – usually without a scar.
Itching caused by infection is generally localised (see below) one notable exception is scabies – a tiny skin parasite which can spread around the whole skin. In patients who have a reduced immunity this is not uncommon particularly seen around the trunk.
Causes of localised itching
Long standing skin conditions. Eczema, Psoriasis,
Contact dermatitis. A itchy rash which looks like eczema the skin is thinned, looks sore, reddened and cracked. It usually occurs on the hands but can occur on any part of the body which comes in contact with the substance which is causing the reaction. Substances which most commonly cause a reaction include skin creams, cosmetics, washing up liquids, detergents.
Localised Infection Herpes – particularly around the mouth,
Shingles in a band around the body usually on on side – The itching often starts before the rash which is often associated with pain which may last several months.
Local infestation with lice or scabies particularly around the naval or between the fingers, local thrush infection particularly in the groins or skin creases (check for diabetes).
Cutaneous involvement with tumour. The skin is raised and nodular, can be reddend or have a purple tinge (violaceous) if severe ulcers will also appear. On the chest wall – this is mostly associated with breast cancer, If widespread across the whole body lymphoma is often the cause.
General measures ro relieve non-specific itching
Before offering advice or treatment the cause should be known. Sometimes specific treatments are available otherwise here are some general measures which may help:-
Creams – hydrocortisone (0.5 – 1%) Available over the counter but best prescribed by your doctor. Urea based creams or bath oils are often affective – eg balneum plus.
Tablets – Antihistamines can help, occasionally a low dose of steroids are required.
Clothes – Ensure clothes are well rinsed to remove as much detergent as possible. Avoid tight fitting clothes or over heating. Loose cotton is ideal rather than wool or synthetic based linen.