Echinacea is a plant that is sold as an over-the-counter supplement for the prevention and treatment of the common cold. Many preparations are available including different compositions and different extraction methods. A review of studies in the prevention of illness showed no statistical significant improvement in the prevention of the common cold as compared to placebo. In studies comparing echinacea to placebo in the treatment of cold symptoms, results widely varied. One aerial form of the plant, Echinacea purpurea, was found to decrease the duration of the illness and lessen the severity of experienced symptoms. There is, however, no clear evidence that any kind of Echinacea is beneficial for children. In fact, one report demonstrated an increase in the occurrence of rashes among children taking echinacea, as compared to the placebo group.