Symptoms:

• It occurs in area of skin, where the shingles, outbreak first occurred. Most commonly a band pattern around your trunk, usually one side of your body.
• As rash or blisters go away, pain may remain
• Pain that lasts 3 month or longer, after the shingle rash has healed. This pain is burning, sharp deep aching pain.
• Increase sensitivity to light, touch. People can not bear the touch of clothing on the affected area. (allodynia)
• Itching and numbness in the area of rash.
• Pain that is constant or comes and goes
• Pain gets worse at night or in heat or cold temperature.

Causes:

• Once you have chickenpox, the virus remains in your body for rest of your life,.
• As you become elder, or when your immune system is suppressed, such as from medication, the virus reactivate causing shingle
• If your nerve fibers are damaged during the outbreak of shingle, post-herpetic neuralgia occurs.
• The nerve fibers at the skin in the affected area send exaggerated pain signal to your brain..

Risk factor: 

• You are older than 50
• Severity of shingles: if you have severe rash and intense pain
• Associated illness like diabetes
• Shingles location – shingle on face and torso
• Delayed anti-viral  treatment: if treatment is delayed more than 76 hours, after your rash appeared.

Complication:

• It depends on how long PHN lasts and how painful it.
• Other symptoms might be associated with chronic pain
• Depression, fatique
• Difficulty sleeping, lack of appetite
• Difficulty in concentrating
•  

Prevention;

• The centre of disease control and prevention recommend shingrix for adult,, and more than 50.
• 2 dose of shingrix is more than 90% effective in preventing shingles and post-herpetic neuralgia

How PHN is treated?

• Start anti-viral medication( Acyclovir) as soon as the rash appear.. These medications help the radh heal faster, decrease pain and itching.
• Lignocaine 5%, topical application plays a great role in healing.
• Neuropathic medications like, pregabalin, gabapentin for burning pain.
• Anti-depressants medications like Amitryptiline or Escitalopram
• Botulinum Toxin( botox) injection in the area, where you have pain.
• There is no clear cut superior treatment for PHN.
• You may need more than 1 medications for pain relief.