Thank you for the question.
The are many causes for itchy skin when no visible rash can be seen.
The causes include:
1 Dry Skin
2. Underlying skin diseases eg. eczema, hives
3.Neurological causes eg. notalgia paresthetica, shingles
4.Underlying medical problems eg. renal or liver disease, thyroid problems, iron deficiency
5.Certain cancers eg. lymphomas or myeloma
6. Psychological factors eg. anxiety and stress
Often further history examination and blood tests will be required to determine any underlying cause for the itch.
If you have persistent unexplained itch, do see your doctor or dermatologist for a proper assessment and management.