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Dr. David Hill, DC

Founding Executive

Dr. Hill oversees all science, research, medical, and safety departments at doTERRA. He’s known across the world as an expert in essential oils and integrative medicine. 

Dr. Hill, a pioneer and leader, has been a pivotal force for bringing essential oils into the mainstream over the past several decades. He partners with international physicians, scientists, and hospitals, defining and establishing the medical integration and use of essential oils in modern health practices. He guides advances in essential oil science at top universities and research affiliations, helping provide more in-depth understanding of essential oils and their uses. 

Along with his many accomplishments in essential oil science and research, Dr. Hill is also a beloved educator. At the end of the day, his favorite way to spend his time is at home with his wife, children, and grandchildren. 

Dr. Russell Osguthorpe, MD

CMO, (Chief Medical Officer)

Dr. Russell Osguthorpe currently serves as chief medical officer at doTERRA. He’s establishing a network of primary care clinics focused on wellness and prevention through integrative, evidence-based medical practices. He’s also researching the use of essential oils in healthcare settings. 

Dr. Osguthorpe received his medical degree from the McGill University School of Medicine, completed his residency at the Children’s Hospital in Denver, Colorado, and pediatric infectious diseases fellowship at Washington University School of Medicine. 

Dr. Brannick Riggs, MD

Vice President of Education, Chairman of Scientific and Medical Education Committee

Dr. Brannick Riggs was born in Lafayette, Indiana, but he was raised around the world. He’s a board-certified family practitioner. In 2001, he graduated from the University of Arizona College of Medicine in Tucson, receiving some of his training in complementary and alternative medicine. After graduation, he participated in the McKay-Dee Family Practice Residency program, which brought him and his family to Ogden, Utah. 

Dr. Riggs enjoys the full spectrum of family medicine and is a member of the American Academy of Family Physicians. Dr. Riggs served as medical director of his busy practice, as well as for a nursing home and two hospice groups. He was also the northern Utah medical director for Revere Health from 2014 to 2017.  

Dr. Riggs has a strong interest in value-based healthcare and is passionate about changing the profession he loves for the betterment of patients and physicians. He was honored to receive the Patients’ Choice Award for seven consecutive years. He’s now chairman of the Scientific and Medical Education Committee and vice president of clinical initiatives for doTERRA. 

Dr. Riggs enjoys using essential oils in his home and integrating them into his medical practice to bless the lives of patients. When he’s not working, Dr. Riggs and his wife, Juli, enjoy spending time with their five children out in the Wasatch Front. They garden, tend to their small farm, and love to travel the world together. 

Dr. Katherine Igah-Phillips MD, MHA

Integrative Medicine

Dr. Katherine Igah-Phillips—affectionately known as Dr. K—is an award-winning international speaker and holistic humanitarian. She focuses on the power of mental, physical, emotional, and spiritual wellness. 

Dr. K uses her private integrative medicine practice to provide her community with holistic, natural, and authentic medicine, delivered by a team of like-minded practitioners. She also offers a virtual mentorship program, where she creates space for personal development and elevation of consciousness. Dr. K maximizes her life’s purpose by providing necessary tools and coaching for people to access genuine wellness, holistic elevation, and a fulfilling reality. 

Dr. Jessica Herzog MD, FAAP, ABOIM

General Practice

Dr. Jessica Herzog is a leader and teacher in the field of natural healing. She serves on the medical boards of Synergy Science and Infinity Medica. She’s the founder of Blue Pebble Health, an integrative and functional medicine center with locations in Utah and Pennsylvania. Her mission has always been to help others advance on their wellness journeys by uncovering what’s holding their health back. Her team of natural-minded practitioners specialize in recovery from chronic fatigue, autoimmune conditions, digestive concerns, and hormone imbalances. Dr. Herzog’s health philosophy is simple: optimize mitochondrial or cellular energy and provide foundational nutrients. This approach has worked for optimization, recovery, and prevention. 

Dr. Herzog is dual board-certified and completed her undergraduate degree, medical doctorate, and pediatric residency at the University of Maryland. During her studies, she participated in research teams at the National Institutes of Health and the University of Maryland. She started her career as a pediatric hospitalist, serving in Maryland, Utah, and Pennsylvania. For the last 10 years, Dr. Herzog has exclusively worked in natural medicine, acknowledging the power of time-honored herbal and essential oil traditions. She’s also a champion of cutting-edge health technologies, which stimulate cellular energy and pair perfectly with traditional approaches. 

Dr. Herzog whole-heartedly practices what she teaches, striving for the optimal balance of physical, mental, emotional, and spiritual wellness. She uses essential oils daily as part of her personal routine, taking them internally (her go-to method), diffusing, and applying topically. She lives in Utah with her family of six children. 

Dr. Amy Wolthoff, MD

Dr. Amy Wolthoff grew up in Grapevine, Texas (a suburb of Dallas). In 2009, she received her doctor of medicine degree from the University of Texas Health Science Center in San Antonio. Dr. Wolthoff completed her internship year in internal medicine at Texas Health Resources Presbyterian Hospital in Dallas. She then joined the Department of Dermatology at the Texas Tech Health Science Center in Lubbock, where she received the Resident Leadership Award, which recognizes superior leadership qualities, professionalism, teamwork, and dedication in the residency program. She completed her dermatology board exam and became board-certified in July 2013. 

Since starting in private practice in Dallas, Dr. Wolthoff has received many awards from her patients and peers, including “Three Best-Rated Dermatologists in Dallas” in 2016, “Texas Rising Stars” from 2014 to 2017, “Top 10 Doctors” in 2015, “Most Compassionate Doctor” from 2013 to 2017, and “Patient’s Choice Award” from 2013 to 2017. 

Dr. Andrew Gough, DO

Dr. Andrew Gough was born and raised in England to parents who both practiced medicine and believed in the effectiveness of alternative medicine. He completed a sports science degree from Chelmsford College before moving to the US, where he studied psychology and chemistry at BYU–Idaho, graduating with honors. Dr. Gough then graduated from the founding school of osteopathic medicine, Andrew Taylor Still University, and completed his residency in emergency medicine at the St. Joseph hospital system in Detroit, Michigan. 

Dr. Gough currently practices emergency medicine at Sanford Hospital in Aberdeen, South Dakota. He’s passionate about learning, studying, and educating people about the many health benefits provided by doTERRA essential oils and natural products and is dedicated to sharing how they’ve blessed his family and continue bringing hope and healing to so many people worldwide. 

Dr. Chris Spelman DDS

Dr. Chris M. Spelman is a general dentist with a private practice in New Jersey, offering a full scope of dental services. He graduated with honors from the University of Maryland in 2001. Dr. Spelman is a member of the Academy of General Dentistry. He studies essential oils extensively and uses them regularly in his practice. He’s passionate about educating both his patients and colleagues about the importance of living a wellness-based lifestyle. 

Dr. Ashley Anderson NP with PhD

Dr. Ashley Anderson received a Master of Science in Nursing with a Women’s Health Nurse Practitioner Specialty in 2008, a certificate in Health Professionals Education in 2012 and a Doctor of Philosophy in Nursing in 2016, all from the University of Louisville. She received her Bachelor of Science in Nursing from Berea College in 2005. She was a record holding team Captain for Berea College’s Women’s Basketball team. Dr. Anderson participated in beauty pageants to take advantage of additional scholarship opportunities as she pursued her education. She won Ms. Kentucky United States 2013, Miss Black Ohio in 2010 and was crowned the 1st Miss University of Louisville in 47 years when the competition returned to campus in 2008.

Dr. Anderson is the founder and CEO of Athena Health and Wellness, a women’s health practice that is the first of its kind in Louisville, Kentucky. In 2020, she partnered with doTerra and launched an essential oil business to help promote natural healthcare in the western realm of medicine. She is a family planning specialist, trained researcher, author, certified health science educator, community activist, international runway model, actress, radio personality, and motivational speaker.

In 2016, Dr. Anderson was the recipient of the Guy Stevenson Award for Excellence in Graduate Studies, the highest honor the University of Louisville gives to graduating doctoral students. In 2014, she was named Glamour Magazine Phenomenal Woman of the Year for Kentucky. Dr. Anderson is the Executive Director of the Miss Black Kentucky USA Scholarship Organization where she works to empower young black women, through pageantry, to develop the leadership skills, confidence and network to achieve their biggest goals in life. Ashley resides in the Louisville area with her two sons, Atlas and Ace.

Dr. Janet Roark

Dr. Janet Roark is a veterinarian and the proud owner of Hill Country Mobile Veterinary Service in Austin, Texas. She triple-majored for her BS at Ohio’s University of Findlay in biology, equestrian studies, and pre-veterinary medicine, along with minoring in chemistry. Afterward, she graduated from Michigan State University’s College of Veterinary Medicine in 2005.

Dr. Roark began using essential oils for her own health after battling both physical and emotional struggles related to stress. She then used essential oils in her veterinarian practice about six months after integrating them into her daily life. She now specializes in integrating acupuncture and essential oils along with traditional modalities.

Essential oils literally changed her life forever, and she has made it her mission to educate people all over the world regarding the safe and effective use of doTERRA essential oils with animal treatment.

Dr. Jeanette Yamamoto

Dr. Jeanette Yamamoto obtained her bachelor’s degree in animal science from Oklahoma State University in 1997 and received her doctorate in veterinary medicine there in 2002. Returning to California after graduation, Jeanette completed a small-animal internship and worked as a senior emergency and critical care clinician at the Animal Specialty and Emergency Center in Los Angeles until 2012. In 2011, Jeanette established Peaceful Pets In-Home Euthanasia Services to ensure comfortable passings for dogs and cats in her area. She expanded her practice to incorporate hospice and palliative care, focusing her energy on her business full-time. Jeanette earned her veterinary hospice and palliative care certification in October 2020. 

She was introduced to doTERRA essential oils in December 2014, soon becoming a Wellness Advocate, and incorporating essential oils into her general practice and in-home euthanasia service. The essential oils have improved many of her patients’ quality of life and become an important part of her practice. 

Jeanette resides in the Santa Clarita Valley of Southern California. She and her husband, Jeremy, are parents to two wonderful children, Ellee and Justin. They have a cat (Boxsie), a pit bull mix (Bella), a Yorkie mix (Phoebe), and a miniature pinscher mix (Zero). 

Dr. Mia Frezzo

Dr. Mia Frezzo is a veterinarian, wife, and mother of three young children, residing in northern New Jersey. Her passion for veterinary medicine was initiated and fostered by her uncle—also a veterinarian. Mia studied and worked with her uncle since age 14. She graduated from Ohio State University’s College of Veterinary Medicine in 1998, returning home after graduation. 

She is the owner and medical director of the Animal Hospital of Hasbrouck Heights in Hasbrouck Heights, New Jersey. Dr. Frezzo’s patients, primarily dogs and cats, benefit greatly from her combined holistic and traditional approach, emphasizing doTERRA essential oils, natural health, and illness prevention.

Dr. Frezzo became convinced of the power of essential oils through her own personal experience. As her daughter struggled with a health issue, she grew increasingly frustrated with her lack of progress. Dr. Frezzo found doTERRA Breathe and On Guard to be highly beneficial and effective support for her daughter’s wellness.

Dr. Frezzo has proudly and confidently spoken in support of natural doTERRA essential oils and natural products with her family, friends, and clients, both in the United States and abroad. She has seen remarkable improvements in the physical and emotional well-being of her patients, leading to her writing SpOIL Your Pet: A Practical Guide to Using Essential Oils in Dogs and Cats.


Dr. McCaskill grew up in the rural community of Central, Louisiana, located on the outskirts of Baton Rouge. He attended Louisiana State University (LSU), completing his undergraduate. He was commissioned as a second lieutenant in the United States Air Force (USAF) in January 1970, becoming a fighter pilot and serving until August 1977, after which he entered the LSU School of Veterinary Medicine.

While in veterinary school, he joined the USAF Reserves, continuing his flying career on a part-time basis. Dr. McCaskill maintained dual careers as a practicing veterinarian and pilot for 29 years. He is a combat veteran of both Vietnam and the Gulf War. He graduated in May 1981 and opened the McCaskill Veterinary Hospital, a mixed animal practice, in New Roads, Louisiana, in August of that year.

His interest in and study of veterinary acupuncture and Traditional Chinese Veterinary Medicine (TCVM) began at the Chi Institute, located in Reddick, Florida. He became a CVA in March 2009 and is now a certified TCVM practitioner (CTCVMP), which requires certifications in veterinary acupuncture, Chinese veterinary herbal medicine, Chinese veterinary food therapy, and Chinese veterinary tui-na (massage techniques).

He has incorporated doTERRA essential oil therapies into his treatments for small animal patients. He loves promoting TCVM in worldwide presentations and mentoring students who are learning veterinary acupuncture. He is a Chi Institute instructor, teaching acupuncture to students in China.

Dr. McCaskill resides in Oscar, Louisiana, by False River with his wife, Lu, and their yellow Labrador, Cakki. They have two children, Matt and Megan, and five grandchildren. They are active members of St. Mary’s Catholic Church in New Roads. His favorite hobbies are exercising and dove and duck hunting with Cakki.

Dr. Janish Fisher DVM, CVA, CCRT, CAC

Dr. Janis Fisher is a graduate of the Atlantic Veterinary College of Prince Edward Island, Canada. Early in her career, she realized she wanted to take a more holistic approach to well-being. She became a certified veterinary acupuncturist through the International Veterinary Acupuncture Society in 2005. Ever since, her practice has included both acupuncture and traditional Chinese medicine herbal therapy.  

She’s a certified canine rehabilitation therapist and animal chiropractor.  

Her desire for natural solutions led her to doTERRA essential oils. After witnessing the health benefits of essential oils in her home, Janis integrated them into her veterinary rehabilitation practice. doTERRA essential oils are now diffused daily at her office, and she enjoys educating colleagues on the benefits of essential oils for their animal patients. 

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