Not all poisons are man-made chemicals. Many are natural toxins, poisonous substances that are produced by a plant or animal, usually as a defense mechanism. Dumb cane, philodendrons, holly, poke weed, rhubarb leaves, and rhododendrons are among the more common sources of plant poisonings. The number of possible interactions between drugs increases much faster than the number of drugs taken. For example, one interaction is possible with two drugs, three interactions with three drugs, six with four drugs, and ten with five drugs.
Poppy seeds contain small amounts of opiates and can produce a positive test for opium.
While the levels of drugs found in these foods are too small to cause intoxication, they can cause positive drug screening results if they are ingested shortly before a test. These are technically not false-positives, because the drugs are actually in the urine. They can, however, lead to a false conclusion of illicit drug use. Published under license from Houghton Mifflin Company. All rights reserved.