Breath
The breath of a Western dragon is often toxic. This could be because of the venom in their mouths or it could be a product of their digestive process.
Dragons’ breath can poison people and wither plants. Several dragon-slayers were overcome by a dying dragon’s breath—some were revived, some died. Successful slayers took the precaution of using very long spears when attacking dragons so that they could keep out of range of the poisonous breath.
Chinese dragons, on the other hand, breathe mist. The mist forms into clouds and from the clouds comes life-giving rain.