Rattlesnake-weed sap, like that of many spurges, does contain unusual chemical properties. And such plants can have genuine medicinal uses. The spurge family, especially, seems to favor powerful chemicals. A non-native relative, castor bean, yields a bitter concoction called castor oil used to treat gastrointestinal ailments. Other family members contain strong poisons.
Plants normally evolve such toxins as a defense.
And it seems to work. Many plants of the genus Euphorbia, to which rattlesnake weed belongs, show far less damage from insects than other plants. P.O. Box 11626, Santa Ana, CA 92711.