There are many causes of itchy skin but they almost all arise from their skin being dried out.
Some possible causes are:
- A nutrient deficiency in their diet
- Over or under bathing
- Not grooming enough
- Dry climate or house heating
You need to look out for other signs such as biting or skin infections to make sure it is not a greater issue.
Hopefully, if any of the above symptoms ring true, you can isolate the cause and fix the problem.
All the best.