I'm really not so sure that Epsom Salts would do a Fatsia any good but will watch with interest the answers given.

I too doubt that giving your Fatsia Epsom Salts is going to help it...

Epsom salts are applied when magnesium deficiency is present - this shows itself as yellow patches between the veins in leaves which eventually may turn brown. If your leaves are generally yellow, that may not be the cause, so epsom salts will do nothing.
Is it growing in the ground or in a pot and how long have you had the plant? this assumes you're speaking about Fatsia japonica and not Ricinus.

Thanks Bamboo learnt something more...

And the other thing I forgot to mention that makes me think its definitely isn't magnesium shortage is that its the newer leaves which are yellowing - magnesium shortage affects older leaves first.

I don't know why I thought it would help I did have one before and read somewhere it was what it needed and it did but can't remember amount I used. It has lost few lower leaves as well.

Lots of people think yellowing leaves means magnesium shortage, but it doesn't necessarily. Any chance of a photo of the plant?