Postherpetic neuralgia is an unfortunate but potential complication of shingles (or zoster). It is actually not that common in young patients of your age. I would recommend discussing this with your doctor
as there are many treatments for this that are mostly successful.
Shingles (or zoster as its medically known) is an infection that occurs commonly. It is actually a viral infection, with the virus actually being the varicella virus -- the same virus that causes chicken pox. The virus actually lives in the nerves. After an eruption in the skin (shingles) a few patients will have continued pain or sensitivity even after the rash resolves. This persistent pain is thought to be due to nerve damage.
Treatments for nerve damage are mostly quite successful. As you have tried, topical capsaicin and over the counter painkillers are the most common first line treatments. There are other medicines specific for nerve pain. These include anti-seizure medications -- notably neurontin (gabapentin) or pregabalin (lyrica) which work quite well. Tricyclic anti-depressants also work for nerve pain (at doses much lower than when used for depression
). Another medication would be a lidocaine patch -- a medicine that can be placed over the area.
Talk to your doctor.