What Causes Red Spots Within Tattoos?

i had a tattoo about 3 week ago after about 1 week a started getting red spots that look a little like blisters within the tattoo it has not spread any where else i have other tattoos around it but there fine i went back to the tattoo artist and he said it was the chemicals used to clean the equipment and have changed them since told me to use bio oil been using it now for about 3 days and no change. should i be using this? i have lots of tattoos never had reaction before what should i do please?.