Itching, also known as pruritus, can be one of the most distressing physical sensations we experience.
Most of the time, itching is a short-term problem and its cause will be obvious. The red swelling of a mosquito bite, or other insect bite or sting, is easy to see and may cause intense itching for a limited time.
People whose itch is due to eczema or allergic contact dermatitis usually have a rash in the affected area. They will experience recurrent attacks of itching when their problem flares up, but will usually have learnt how to control it with the use of creams or ointments.
When the sensation of itching is present without a rash or other visible cause it can be hard to find the reason and this may make treatment difficult.
Causes of itching
There are a number of possible causes for an ‘unexplainable’ itch without a rash. These include the following.
- Dry skin. Frequent bathing, especially with hot water, along with hot or cold weather, low humidity and central heating or air conditioning, are common causes of dry skin.
- Age. Roughly half of those over the age of 70 will experience itching, and may damage their skin by excessive scratching. With age, our skin becomes much drier and regular use of moisturisers will usually solve the problem.
- Hormonal changes after the menopause. Many women at this stage of their lives experience itching, often associated with hot flushes, which are worse at night. Hormone replacement can produce a rapid improvement.
- Changes in body chemistry. Most people having dialysis (artificial kidney) treatment get pruritus, although the reason for this is not certain. People with liver disease and jaundice, in which the amount of bile salts in the circulation is abnormally high, usually get itching.
- Reaction to water. Some people seem to develop an itch when their skin is in contact with water, regardless of its temperature. This is difficult to treat but may respond to treatment with ultraviolet (UV) light.
- Illness. Certain illnesses such as thyroid disease and some blood disorders may cause generalised itching. Some types of cancer may also produce itching.
- Reaction to a medicine. Some medicines have itching as a side-effect, including some antibiotics, some cholesterol medicines, and pain medicines.
- Pregnancy. Some women experience itching during pregnancy.
- Scabies. Intense itching, worse at night, is a symptom of scabies infection, which is due to a tiny mite. The associated rash may be mild and barely visible.
- Sexually transmitted diseases or vaginal thrush. These can cause genital itching.
- Nerve conditions. Multiple sclerosis, shingles and other conditions which affect the nerves can be the cause of itching.
If you get recurring feelings of itching and can't see a cause, discuss it with your doctor. It is possibly a warning of some other problem and can usually be relieved.
Complications of itching include loss of sleep, and injury and infection to the skin if it is scratched. And potentially scarring caused by scratching.
Treatment of itch is usually directed at resolving the cause of the itch. If the cause cannot be found, then treatment with emollients (soothing or softening skin preparations), oral antihistamines, or steroid creams may help.
Phototherapy (light therapy) sessions, where your skin is exposed to certain wavelengths of ultraviolet light, may help. Phototherapy should only be done under the direction of your doctor.
2. Mayo Clinic. Itchy skin (pruritus). http://www.mayoclinic.org/diseases-conditions/itch-skin/basics/definition/con-20028460 (accessed Sept 2015).