Hello,
Thanks for posting your query.
In order to provide you with the most probable diagnosis I would require a few clinical details as follows,
1. Appearance of rash maculopapular( reddish pimple like ) or fluid filled vesicles or tiny blisters or pus filled etc
2. Any history of fever , weakness , itching or pain or associated with the rash .
3. Any past history of allergy or immune disorders or on any immunosuppression drugs like steroids etc
4. Any medical illnesses like thyroid , diabetes etc and wether taking any daily medication.Undergone any surgery in recent past ?
5. Dissapearance of rash was after any particular treatment or self resolved ?

Assuming you have no major details to provide and the fact that you have suffered from shingles makes it most likely to be a herpes simplex reactivation rash which usually follows a particular pattern along nerves ( dermatomal) like across arm or thigh or chest etc.
This may cause burning or painful sensation even after the rash has gone . This is called post herpetic Neuralgia .
It's very common condition in elderly and immunosuppressed individuals and the treatment includes local ointments and oral antiinflammatory analgesics etc
However if not treated it may cause significant discomfort to the patient .
Also this condition has a tendency to recur in future.

So the best next step would be to consult the lady's dermatologist who can confirm the diagnosis after thorough evaluation and start appropriate treatment .
It's not necessarily to rush over it since the rash has been since last 2 weeks and has not shown any complications like fever , pus etc but it's definitely best to get it treated than neglect it .so please do not worry and do the needful .
Hope I have answered your query.
Kindly accept my answer in case you have no further queries.
Wishing her a speedy recovery.
Regards

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Hello,
Thanks for the details . It certainly seems less likely any serious infection and more of a dermatitis either eczematous rash or less likely a fungal infection.
Since it has responded well to calamine and dry powder ( J&J) and had associated itching it is mostly just a dermatitis which usually should resolve if the irritant cause is removed .
So first and foremost try to look for any new change in terms of contact clothing or any chemical ( soaps ,creams , powders etc).
Assuming there is no known source and is mostly an idiopathic eczema it should resolve with calamine and dry powder application.
If it still persists then local application of mild hydrocortisone cream might be beneficial but it's best to get it prescribed by your doctor after confirmation of the diagnosis .
In case the lesions show further spreading your doctor might rule out a fungal infection and if suspected give a trial of antifungal dusting powders like clotrimazole or ketoconazole .
As of now any eczema is best treated by avoiding the irritant , avoiding scratching , keeping the region clean , dry , open frequently and application of zinc based calamine spray or lotion & if necessary oral antihistamine medicines like hydroxyzine or fexofenadine .
So please don't worry and though it seems to be spreading its likely that the rash would respond well to the local home treatment you have started and should resolve in another week . If not then you need to consult your dermatologist for confirmation and appropriate treatment like steroid cream or antifungals and antihistamine medicines ( relieve itching and redness.)

Hope I have answered your query.
Kindly accept my answer in case you have no further queries.
Regards

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