Welcome to HCM.
Parasites which can be spread by skin to skin contact are usually infestations like ticks and lice
. These parasites can cause itchy bumps all over the body due to their bites.
I also agree with your friends treating doctor that he is suffering from delusions as the symptoms he has described do not co relate with any parasitic infection
I suggest you get in touch with a skin specialist for examination and treatment of the infestation if present.