I think to much credence has been put on the allergy side of things since people have a hard time accepting that the vast majority of colubrids are technically venomous. It is a venom, not a toxic saliva.
Similarly, much has been made of H. gigas having an LD50 around that of Crotalus adamenteus. C. adamanteus has fairly weak venom, with the estimated human lethal dose being greater than 100 milligrams. Obviously an amount a false-water cobra would hit. It would be lucky to produce 10 mgs and normally would actually only deliver 1-2 mgs.