Hello,
Without examination it is very difficult to confirm a diagnosis, but the symptoms are suggestive of contact dermatitis(allergic or irritant) , allergies, sweat dermatitis ,eczema or hives.As you had a previous history of hives at the same area,hencethis has a strong possibility.
Take some over the counter oral antihistaminics like benadryl or Claritin,Sometimes they are required for prolonged periods.Since benadryl causes drwsibness so can be used at night to get urticaria control. Short courses of oral cortisone or steroids are taken for short periods (one to three days) to settle more severe symptoms.Application of calamine and mild steroid cream like dermacort will also help in controlling itching.
You may take Vitamin C along with the prescribed treatment. Vitamin C is a general anti-allergy supplement. It helps stabilize mast cells so they are less likely to release histamine.
If the symptoms become severe,then it can be a case of chronic urticaria which needs further evaluation as it may be due to auto antibodies.A dermatologist’s evaluation is mandatory.
Hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional doubts.
I have no clue what it could be, but if your in that much discomfort, then I think you should go to your local drug store, and get some cream or loation for it. You should ask the pharmacist what they think you should use first, and should probaly go to walk-in clinic to see what they have to say because you definitaly dont want to be putting random-ness on your rash.