In that time, he has become an acknowledged expert in the field, lecturing all over the U.S., and internationally in such countries as Canada, Great Britain and Spain. Christopher's specialties include herbs and the immune system; adaptogenic herbs, Native American uses of herbs, the pharmacology and chemistry of herbal medicines, herbs for the liver and the botany and taxonomy of herbs.
Christopher has taught or lectured at universities and medical schools such as Stanford Medical School, Yale Medical School, Bastyr University and the National School of Naturopathic Medicine; including on-going classes at the University of California, Santa Cruz.