Does dishwashing soap need to be kosher certified?

Does dishwashing liquid need to  be kosher? Strictly speaking,   dishwashing liquid is not edible, it is not  fit for human consumption, and therefore,   hypothetically even if it had any non-kosher  ingredients, it would not make the dishes   non-kosher, and they would not become treif.  On the other hand, Rav Belsky ZT"L used to   encourage people to buy kosher dishwashing soap.  You would say, you know, even if it isn't kosher,   you don't want it to get on your dishes and to  get into your food. It's like a level of extra   carefulness, even if it's not edible, it's a  good custom. Most of the dishwashing liquids   do have the OU and those ones therefore don't have  non-kosher. So that is something a person should   be careful about if they can. If a person bought  a dishwashing liquid that does not have an OU,   they could use it. It's not going  to make their dishes non-kosher.