Sevin is just like anything that is applied topically...it is absorbed internally. The skin is the biggest organ our body has and you would not believe how effective it is for absorbing things in our shampoos, lotions, bug sprays, etc. Whatever you would not like to eat in the eggs, I wouldn't place on their skin.
Better deworm the kids!
When I was little it was pretty accepted that everyone got worm medicine for pin worms each spring...and we did. Wonder where all those pin worms disappeared to from that time to this? You can safely figure that, if your animals have worms, the kids do too.
Ivermectin is just a pretty harsh thing to give, no matter what the vet may say. Think about it...this is something you can pour on the back of a cow that will absorb into their skin and into the blood stream and consequently kill the parasites in the bowel. Poisons them. What do you think it's doing to the animal? Not to mention that using these kinds of dewormers on a regular basis can promote worms that can survive the biggest, harshest dewormer out there. These are the survivors. They will bear offspring that are resistant to the Ivermectin. If they can survive the Ivermectin, they most certainly will survive the less harsh chemical dewormers. Where do we go from there?
Many people in the livestock world are finding this out, which is why they keep coming out with newer and worse poisons to poison the generation of parasites that survived the last bad poison. The people who are tired of this cycle are looking for ways to control parasites without creating the "super worm". Same concept as the overuse of antibiotics.