Chrysanthemums contain a natural insect repellent called pyrethrum. Researchers are studying ways to increase production of the flowerheads, which contain the most pyrethrum.
Pyrethrum, a natural chemical found in chrysanthemums, can repel insects like mosquitoes and ticks. Pyrethrum can be used in dog shampoos but not cat shampoos as it's toxic to cats and has to be dosed just right for dogs.