Dominance involves one allele masking another at the same locus whereas epistasis involves one locus masking a different locus.
Explanation:
Epistasis is a type of gene interaction in which one gene masks or modifies the expression of another gene at a distinct locus.
Dominance refers to the gene interaction in which one allele of a given gene masks the expression of another alllele of same gene.
The comparison of dominance and epistasis give the following information: