Please don’t confuse the normal effect of venom with the anaphylaxis. Heat can disrupt the venom, but may not destroy the allergy-triggering antigen on the peptide. So if you are not allergic, the heat (etc.) should work. If you are allergic, what you are reacting to on the venom peptide may or may not be disrupted by the heat.
Immunology and antibodies are pretty complicated, but many proteins/peptides are similar between species, including venoms. If the peptides are similar enough, it may be that exposure to foxface venom sensitized you to the venom, which then cross-reacted with the lionfish venom.
As above, wear arm length gloves if you must keep the venomous fish. Have the epipen with you whenever working on the tank.
Immunology and antibodies are pretty complicated, but many proteins/peptides are similar between species, including venoms. If the peptides are similar enough, it may be that exposure to foxface venom sensitized you to the venom, which then cross-reacted with the lionfish venom.
As above, wear arm length gloves if you must keep the venomous fish. Have the epipen with you whenever working on the tank.