9 causes of itchy skin

Rather like yawning, itching is outrageously catching. Go on - try it! Think about something itching you and you'll be scratching away in a flash.

Most itches are localised to one part of the body and tend to come and go fairly swiftly. Occasionally, itching becomes more generalised and affects larger areas of skin, if not the whole body. If it goes on for six weeks or more it is called 'chronic pruritus'. This is a most unpleasant phenomenon and can drive people to distraction, affecting sleep, concentration and even mood. There are many many causes of chronic pruritus but I've compiled a list of some of the important culprits:

1. Skin conditions, such as eczema, are a common reason people are itchy. Eczema can affect large parts of the body and often results in very dry and itchy skin

2. Skin infections such as scabies are well known to cause a maddening itch. Other more serious infections such HIV can also, rarely, cause itching of the skin

3. Certain blood disorders, such as lymphoma, may cause widespread itching. This sort of itch is often worse at night

4. Blood testing can be a useful investigation into the cause of chronic pruritus. Liver and kidney upset can result in itching, as can imbalances in thyroid hormones and low iron levels

5. It is always worth considering medications when it comes to a whole body itch. Aspirin and penicillin can classically cause an itch, usually alongside a rash. However, a multitude of other drugs can induce itching. Common culprits include: certain blood pressure medications, antidepressants, some diabetes tablets, anti-inflammatories, the contraceptive pill, statins and treatment for gout

6. Rarely, serious psychiatric conditions can cause patients to itch. Schizophrenia,eating disorders and depression are all know to cause itching

7. Many people become itchy during pregnancy. For most this is a minor inconvenience, but some people develop 'acute cholestasis of pregnancy' which causes intense itching

8. Many of us develop fragile and itchy skin with advancing age

9. In 10% of cases the cause of itching is never known.

Dr Jessica Garner is a GP and health blogger. Visit her blog here.