Hi S f S, I'm not decrying your 2,5 pentanedial, but when you have a flock of 100 sheep+ it is not practical to check them all for orf scabs, let alone apply it. The sulphur + salt allows them all to treat themselves and ensures it does not recurr. Applying an ointment may cure those you see at any one time, but not does stop it affecting the rest. Once you have got orf it can spread throughout the flock for the next few months unless you treat them all at the same time. In addition, you do not want to be handling sheep with orf because, like you say, it can be caught by humans. I know - I've had it.