20minutes???? never heard of that!
I've had to use epsom on so many things.
Constipation: left until they pooped their little guts out
and boy, they poop!
SBD: One boy I had battling for a few months. on and off epsom because we had to break it inbetween doses since it should only be 10 days. 3 months! We were worried it was chronic - so we left him in it again and finally it cleared up with no feedings for a couple weeks D: he is the meanest healthiest booger now.
popeye and blistering areas: it seems to help sooth, avoid infections, and drain the fluids. Can be done for those water pockets (forgot the actual name for it) as you should never drain it yourself...
So if it is the last one, it should work. One teaspoon per gallon, up'd to 3 teaspoons per gallon. Hence the large number
I've never had a negative problem with epsom as long as it is thoroughly dissolved beforehand. 20 minutes won't give it time to kick in - it can be 1-3 days before any signs usually - or in severe cases, 5-10 days.