Anti-Inflammatory Effects of Counterirritants

¹ From the Department of Chemistry, Northwestern University Dental School, Chicago, Illinois

Experimental inflammatory edema was induced by injecting an irritant solution into the pleural cavity of rats. The volume of fluid found in the pleural cavity after a specified time interval was used as a measure of the degree of inflammation produced. The effect of counterirritants on reducing pleural inflammation was studied. Injection of irritants into the knee joint of the rat was found to reduce the amount of pleural inflammation formed. The anti-inflammatory effect observed could not be explained by loss of fluid into the injected knee, nor by stimulation of the pituitary-adrenal axis. The effect was still present in hypophysectomized rats and adrenalectomized rats. The use of plaster casts to prevent fluid loss into the injected leg did not block the reduction in pleural inflammation. It was suggested that counterirritants release some substance or substances from the tissues which they damage, which is carried by the blood and can exert an anti-inflammatory effect in another part of the animal.