Infant botulism is a very rare but serious form of illness that can affect children up to one year. It is caused by a bacterium called Clostridium botulinum . This bacteria forms "spores" that when swallowed may grow and produce a poison in the baby's intestine. C. botulinum can be found in both pasteurized and unpasteurized honey. Therefore, it is very important to never feed honey to a child under the age of one. As the spores are not easily destroyed by heat (for example by cooking or boiling), it should also not be added to infants' food as a sweetener. C. botulinum can also be found in soil and dust.