If you Google "Hoppes 9 MSDS" you will find it to be:

30 - 40% kerosene,
30 - 40% ethyl alcohol,
and less than 10% each
xylene,
amyl acetate,
ammonium hydroxide,
and citronella.

Research each of the above chemicals and decide for yourself.

I was advised by the gun shop where I bought them not to use Hoppes on my nickel guns so I don't tempt fate by poo-pooing the advice. I clean all my guns with Ballistol and polish the plated ones with Mothers Chrome polish. Works for me.