Flea concern for dogs :/

I just wanna get some opinions from others - if i go to someones home and their pets have fleas, how likely is it that ill bring them home to my dogs? Im absolutely petrified of parasites and give my dogs a preventative every other month and i treat my yard religiously which seems to work very well...im just super scared about bringing them home from my relatives house! Any ideas? Am i being too paranoid? :(