Yes, this is true especially if someone is sensitive to it. I see alot of posts of chicken owners wanting to use ivermectin products strictly to kill lice/mites. I normally dont recommend a wormer for that purpose and if I do it's only as a last resort. Wormers should be used for just that, worming. I also believe it's even more revelent when it comes down to using antibiotics on chickens, IMO they should be used as an absolute last resort (not to mention bacterial resistance which is also true for wormers.) Penicillin is a good example, it has been used in chickens against severe infections...we know there are people allergic to penicillin and residue could possibly be carried over into the eggs as well as the meat, but I dont know that for fact and I might be dead wrong about that. However, I figure if a chicken is that ill, it probably isnt laying eggs and anyone with common sense ought not eat the chicken neither...but you never know. Then again there are other products such as corid that have no egg withdrawal. It's used in cattle, in chickens for coccidia. I'm sure there are many many products used on chickens, not meant for chickens, that people use including natural products that may show signs of sensitivity in humans that people may or may not be aware of depending on the severity when they do or do not realize it. Actually this can be true for anything we eat, oysters make me deathly ill for some reason and I used to eat them all the time. Someone recently posted a withdrawal list for just about every med that has been used on chickens and I didnt write it down for reference, darn it. Maybe someone will come up with it again....