It's great that you're asking this, as cross-contamination with utensils can cause reactions. If you wash/rinse the peanutty utensils before you put them into the dishwasher so that the peanut butter isn't stuck on, and if the dishwasher soap you use is regular and not organic (natural detergents don't contain bleach), then there's a better chance that the allergenic proteins will be denatured, or neutralized.
no subject
I like this site. Hope you find it interesting:
http://www.calgaryallergy.ca/aasubject_index.html