I have reappearing rash on my abs underarms and elbows hydrocortisone cream seems to help but it reappears after a few weeks

If . If you are dealing with eczema or a dermatitis then it will come and go. We call this a flare up or an exacerbation. Hydrocortisone is helpful, however if it fails to work see your doctor for an evaluation and treatment with a higher potency steroid. Also keep your skin hydrated/moisturized with heavy creams like eucerin or aquaphor. Vaseline also works very well. Take care.