Effect of cromolyn sodium and of daily exposure to compound 48/80 on experimental asthma.

Guinea pigs were exposed to aerosols of histamine or the mast cell degranulating and histamine releasing substance 48/80. Cromolyn sodium aerosols prevented 48/80 induced asthma but did not influence histamine induced broncho-constriction. 48/80 given daily for 5 days resulted in marked decrease in susceptibility to 48/80, possibly because of depletion of histamine and other active substances. There was no change in histamine sensitivity. After 3 days of rest, normal susceptibility to 48/80 returned.