Does using toner cause pimples on the face? Or does it open the pores of the skin? Since using this product, my pores have opened and red pimples have appeared on my face

No it shouldn?t and it probably means your skin is reacting to it. Make sure you aren?t using lots of products on top of this one as well since it?s meant to be used after you wash your face to tighten pores if anything and clear up your skin but everyone is different.