The reason it says that on the label is because it has not been approved for use in laying hens. It hasn't been given a withdrawl period. Some people say 2 weeks but the reason the label says, once wormed with wazine, the eggs are no longer edible ever, is because no studies have been done on poultry and retention time of the active ingredient (piperazine) in egg layers that are used for human consumption. It's a liability issue.Problem is, apparently you can't eat eggs from chickens that have ever been treated with Wazine?