Lime can be an effective flea killer when used on a lawn. When it comes in contact with the pests' exoskeletons, it dries them up.
While lime kills fleas, it should only be used as a last resort when all other methods fail. This is because the amount required to treat a lawn can also have detrimental effects. When grass soaks in the powder, it shrivels up and dies because all of the chlorophyll dries up.
For those with animals or children, it is also wise to avoid using lime in the yard. Its effects can severely dry out and crack the skin. Also, when accidentally ingested or inhaled, it becomes a poison that can make pets and children very sick. If not treated right away, the potential consequences range from difficulty breathing to death.
If someone has no alternative other than to use lime for flea control outside, the yard should be off limits to pets and children for a couple of days. This gives the lime time to dissipate as it soaks into the grass and other vegetation. As an extra precaution, a sprinkler or garden hose should be used to rinse away any excess residue in the yard.