I brushed my teeth and then dissolved a zinc tablet in my mouth.
Afterwards I wondered, would the F- ion in the toothpaste combine with the Zn2+ ion in the tablet, which is not very soluble in water, and would neutralize both the teeth hardening and cold-fighting properties?
It says on the zinc bottle not to drink citrus juices but I cannot find any reliable information online that explains why.
Specifically this form of zinc is not harmful to ingest in small doses. It may cause sight stomach upset, but seems to counteract viruses in the throat.
There was an inhalation version but it is no longer recommended because it causes loss of smell for some people.