A randomized, placebo-controlled, double-blind study evaluated a standardized extract of the aerial parts (containing 4% andrographolides) in the prophylaxis of the common cold in 107 schoolchildren during the winter season. The children received either 200mg extract or a placebo daily for 3 months and were evaluated weekly by a physician. There was no difference in the occurrence of colds between the two groups during the first 2 months of treatment. However, after the third month of treatment, there was a significant difference (P < 0.05) in the occurrence of the common cold in the treated group (30%) as compared with the placebo group (62%) (19).