Does this have a waterproof backing? I'm looking for some pads to do a castor oil poultice. I don't want it leaking through the back.

Yes it does. I had an open incision that was draining and it prevented all that from leaking through the pad. That won't prevent fluids from dripping off the edges if you don't tape them down though.

what is the packed dimension of the indivisual pack?

I bought these last year for my dog. He had a growth on his side and it worked well. It is very absorbent and it covers nicely. I believe the measurements were very true to size. I used it folded in half for coverage but opened up it was very large. I’d say the 8 x 10 on package is pretty accurate. Hope this helps you.

Is this product made in the USA

The package shows that the product is made in the USA.

Are these pads breathable?

I would like to believe that they are breathable and Dermacea™ abdominal pads are designed for maximum absorbency and comfort. Thus, All four edges sealed to prevent lint residue and leaking. Indications include: Primary layer for heavily exudating wounds Secondary layer for heavily exudating wounds Padding for pressure points Anywhere high absorbency is needed I hope this assists