You should not try with another person's dog for many reasons including your safety. Also yes you can can worms in this scenario. Dogs lick their buttholes, and then lick their penis, and they can transfer parasite eggs into you during oral or penetration. Male dogs lick their penis regularly like cats bathe themselves. You can get worse as well. That dog is probably getting parasites regularly because he has a bad habit like drinking from mud outside. That mud gets transfered onto the penis as well and there's plenty you can get from that. You should try to have sex with a dog that you can promote cleaner habits with (because he's your dog).
Unfixed male dogs produce a constant drip of smegma. When the dog can't lick himself because he has a cone on then the penis area becomes covered with white crust. You never see the white crust because dogs keep licking it off before it gets a chance to harden into a crust, given the opportunity.
