What can I do about itching due to Accutane?

I agree with the views expressed by the other doctors. Oral steroids have anti-inflammatory effects and can help your cystic acne and rash. However, long term use can cause a lot of other side effects and it is not recommended as the treatment for cystic acne. In fact, with continued use, you may notice even more acne lesions appearing as long term steroid use can aggravate acne. There are many other good treatments available for cystic acne. You should also get your other skin rash examined to determine the cause. While it responds to steroids, it again is not a recommended long term.

I know how frustrating it is to face the issue of persistent acne. There is no real evidence that skin gets resistant to topical products but obviously anecdotal accounts would suggest otherwise. To cut it short, it sounds like you might need some oral medications like doxycycline or isotretinoin to improve the acute flares first, while using a appropriate skin regimen. From personal experience myself, when facing a flare we tend to overdo things, be it using OXY 10 five times a day and having chemical burns, or washing our face 10 times a day.