Enlarged pores on the back can be caused by a variety of factors, with one of the more common triggers being mite parasites.
Due to the structural limitations of the human body, it is more difficult for the body to clean itself off the back and therefore does not clean it enough. This can lead to a large accumulation of oil on the back, which can easily allow mites to parasitise and induce severe skin lesions, which can even lead to enlarged pores.