Was just looking to see what the active ingredient was in Hartz and came across this site
http://www.hartzvictims.org/ - maybe it was the Hartz. Everyone seems to recommend bathing in Dawn Dishwashing liquid. I even came across one mention that Hartz reimbursed the owners for the vet bills!
From the EPA:
Signs of individual animal sensitivity which may occur after use of this product include skin irritation or hair loss at the application site, salivation, tremors (twitching of muscles), and in some circumstances, severe full body tremors. If this persists please contact your veterinarian and notify Hartz at 1-800-275-1414.
Animals should be observed after application for any sign of sensitivity. If signs of sensitivity occur, bathe your pet with mild soap, rinse with large amounts of water, and consult a veterinarian immediately.