Why is milk or raw egg used as antidote in case of heavy metal ion poisoning?

Answer 1

Egg white isn't an ANTIDOTE for lead posioning, it is a PROPHYLACTIC intended to PREVENT lead poisoning.

Lead posioning occurs when lead enters the bloodstream and binds to proteins in the body. Egg white is itself a protein and if it is swallowed soon after lead is swallowed the lead will bind to the egg protein in the gut and be harmlessly expelled.

It isn't an antidote since it won't help one little bit once someone has lead posioning. It is a prophylactic, a treatment designed to prevent someone developing poisoning.

Egg white also won't help one bit if the source of exposure is through skin conatct or fumes rather than through swallowing.

tc