Why there is no medicine to stop progression of ild without side effects ?whats the best that can be done.death can be avoided completely?

Self-perpetuating: You are referring to common hamman-rich fibrosing alveolitis, correct? Lately the physics that keeps interstitial lung disease going was worked out; the fibrosis that has begun puts an extra stretch on areas of the alveolar walls and by its nature damages them, perpetuating the process. Your best hope is to find a treatable underlying cause though generally there is none. I'm sorry & wish u luck.

Difficult to Dx & Rx: Medical science is struggling to identify the cause of certain ild's and hence they, in general, are a difficult group to treat. Though some ild's respond very well to treatment.