Summary

The "common uncommon" annoying itch between the shoulder blades

Few people shrink away from a nice back or shoulder rub. But some people find the need to scratch their backs becoming compulsive and almost never satisfying. 

One person scratching also triggers mirrored behaviour in others to scratch. But when does the itch become a problem needing further assessment? And who do you ask for advice?

Most people go to their GP, and from there perhaps to a skin specialist - the dermatologist. Often topical creams, with various active agents like capsaicin, menthol or cortisone, are used. It seems most of these give temporary or partial relief. 

This condition may remain undiagnosed for many years as the itch continues, fluctuating for apparently on one or other variable - but seldom consistently. The scratching also persists, resulting in discolouration of the skin that is associated with chronic pressure  or irritation. This is a normal consequence of rubbing - as is seen on the back around a prominent vertebra that presses on a chair - the skin gets discoloured.

Then one day someone says "I think you have notalgia paresthetica". This is the term given to exactly this situation - an annoying, persisting itch between the shoulder blades for which there is no other medical cause. Its cause is unclear as it is relatively rare. How many people suffer this complaint is also unclear because it is not life threatening. When it is mild or moderate it is tolerated to some extent with varying interventions. 

No systematic survey of itch exists. And itch itself is a phenomenon that is only now, in recent years, being better understood.