UPMC University of Pittsburgh Mecical Center "You have allergies to Gold, perfume, soap and your own money!" says the UPMC Dermatology Dept. Pittsburgh, Pennsylvania

I developed my allergy to perfumes in my 40''s.  If I walk into a department store and the blast of air directed out the door, includes the volatiles from the perfume counter, I will almost always, about a day later, develop a burning sensation, and glowing red rash across my face and forehead that lasts for a couple days.  If i wash a pair of jeans in Gain detergent, then put them on, I will get an intensely itchy line (hives) anywhere where the seams contact my skin...in about a half an hour. If I take an antihistamine (long acting like Clarinex) it will prevent these reactions.  I almost never have these reactions since I began only using non perfumed agents.  Incidently, I had an allergist do skin testing and the reaction to pachuli (sp?) was intense.

But there are other causes for widespread itching (urticaria) including liver disease, renal failure, scabies (although not typically involving the scalp) or other skin parasites (lice) - the dermatologist should have diagnosed those things..also systemic infectious diseases usually viral although itching there is usually transient or, rarely, systemic mastocytosis (skin lesions are usually pigmented and there is dermatographia) or some types of porphyria and occasionally seen in hemolytic syndromes.  I'd start out with liver and kidney function studies and a CBC with diff and peripheral smear exam if a perfume free environment isn't changing anything.  

Misdiagnosis; or side effect of aging and inefficient malfunctioning immune system? In October, 2012, I was involved in a minor car accident which significantly sprained my thoracic and cervical spine. Since then the questionable  "shingles" symptoms have increased from covering 15-25% of my skin to approximately 65% of my skin (scalp, chest, arms, legs and mid & low back (initiated by UPMC's dermatology tests?))!  The sleep alterations with the constant urge to itch has me finally understanding why growing old is  really painful.  This doctor is a lousy patient, who wants answers.  A reoccurring sub cutaneous virus? Such a supposedly simple answer to such a painfully irritating condition.  Or next I'll be told by "profiteers", "Its a newly developed allergy- to the air you are breathing."

Shingles is always (95% of the time) on one side of the midline and usually involves contiguous dermatomes.  I've never heard of it occurring in the distribution you describe.  What you describe is more likely contact dermatitis - and if you reacted to perfumes in those tests, it's likely the culprit.  Perfumes are present in a lot of things, and soap and laundry detergents as well as fabric softeners are very commonly the cause of contact dermatitis.  Change the brands you use and get "perfume free" detergents etc.  Use plain Ivory soap and eschew any colonges or deoderants that have a lot of perfumy odor. Throw out the Febreeze if you are using it.  Eliminate anything else in your environment that has a perfumy odor.   Worth the try.  It is NOT shingles...I'd almost guarantee you that!