Edmond (405) 607-4333

Yukon (405) 265-1949

Norman 405-928-1103



Friendly and Caring Staff

We treat you like part of the family!
If you are visiting our office with children in tow, be sure to utilize our kids corner equipped with toys and movies!

Heading photo


CEO / Medical Director / Board Certified Allergist

Dr. Darter received her medical degree from the University of Oklahoma College of Medicine where she was an Alpha Omega Alpha honor graduate. She completed an Internal Medicine residency and chief residency at OUHSC as well. She holds the honor of being board certified in both adult and pediatric allergy, asthma and immunology. She trained at the University of Texas Southwestern in Dallas at Children’s Medical Center of Dallas, and at Parkland Memorial Hospital; one of the most elite training programs for clinical allergy, asthma, immunology and clinical research.
Dr. Darter remains cutting-edge and up-to-date in her sub-specialty by holding professional memberships in a host of professional organizations. Dr. Darter has numerous scientific publications and frequently lectures to other physicians around the world regarding various allergy, asthma, and immunology topics. Dr. Darter also has the honor and distinction of being a Fellow in the American Academy of Allergy, Asthma and Immunology and the American College of Allergy, Asthma and Immunology.
Dr. Darter has resided in the Oklahoma City/Edmond community since 1993. She has three daughters and enjoys spending quality time with them. Dr. Darter also enjoys exercising, especially running, and numerous other outdoor activities.

Heading photo

Jason M. Bellak, MD, FAAAAI, FACAAI

VP / Board Certified Allergist

Dr. Bellak is board certified in pediatric and adult allergy and immunology as well as internal medicine. He knows what allergy sufferers face having eczema, allergies and asthma himself. He is passionate about teaching his patients how to live with allergies and asthma without limitations.
Dr. Bellak is a native of Las Vegas, Nevada. He graduated with honors from UCLA before returning to Nevada for medical school. After medical school, Dr. Bellak completed his internship and residency in internal medicine at the Mayo Clinic in Arizona. He moved to Wisconsin to complete allergy, asthma and immunology training at the University of Wisconsin (UW). While at UW, Dr. Bellak trained under Dr. William Busse, chair of the National Heart, Lung, and Blood Institute expert panel on asthma diagnosis and management, Dr. Robert Lemanske, past president of the American Academy of Allergy, Asthma and Immunology (AAAAI), and Dr. James Gern, who conducts several NIH-funded studies to define the role of viral infections in the initiation and disease activity of asthma. During his education and training, Dr. Bellak participated in multiple laboratory and clinical research studies. Dr. Bellak is a fellow of the American College of Physicians, and a member of the AAAAI and American College of Allergy, Asthma and Immunology.
Prior to moving to Oklahoma, Dr. Bellak had a State of Wisconsin grant to provide primary care and specialty allergy and immunology care to an underserved community in rural Wisconsin. During his tenure there, Dr. Bellak served as medical director of the family clinic and chief of staff while being active in the community providing free asthma and allergy screenings and serving on a community task force to limit prescription drug abuse.
Dr. Bellak, his wife, Jennifer, and his three children, Isabelle, Hunter and Tyson, have established firm roots in Oklahoma. Dr. Bellak and Jennifer enjoy competitive running and spending time as a family outdoors.

Heading photo

Nalin UG, DO


Dr. Nalin U.G. was born and raised in Oklahoma City where he graduated from Classen School of Advanced Studies. He was awarded the Gates Millennium Scholarship to attend Knox College in Illinois. Dr. U.G. received his medical degree from Oklahoma State University, where he was a part of Sigma Sigma Phi. He then completed his training in Internal Medicine at University of Nebraska Medical Center in Omaha. Dr. U.G. trained in both pediatric and adult allergy, asthma, and immunology at Children’s Mercy in Kansas City.
Dr. U.G. is board certified in Internal Medicine. He is also a member of the American College of Allergy, Asthma, and Immunology and the American Academy of Allergy, Asthma, and Immunology.
Even though he spent a lot of his time training outside of Oklahoma, he always wanted to come back to Oklahoma and serve this community. In his free time, Dr. U.G. enjoys biking, jogging, and spending quality time with his family and friends. He is married to his longtime sweetheart, Gigi.  

Heading photo

Andrea L. Sestak, MD, PhD

Pediatric Rheumatology

Dr. Sestak grew up in Edmond, where she graduated valedictorian of the EMHS class of ’85. After college at Trinity University, she obtained an MD and PhD from UT Southwestern in Dallas. She did her pediatrics residency in St. Louis, and then completed a fellowship in pediatric rheumatology in a joint program between UTSW and OMRF. Initially focusing on research, she stayed here and continued work on the genetics of lupus in children until 2010, at which point she turned to the clinical side of her training and joined the staff at OU Childrens Physicians. She is board certified in Pediatrics and a fellow of the American College of Rheumatology. She looks forward to continuing to care for children with arthritis, lupus, and other autoimmune diseases here at OIAAI.

Andrea loves spending time with her daughter, Mikaela, and singing with the Windsong chamber choir.

Heading photo

Kayla Matthews, APRN-CNP

Nurse Practitioner

Kayla is a Colorado native who moved to Oklahoma 12 years ago to attend college at Oklahoma Christian University. After graduating with her Bachelor of Science in Nursing in 2012, she decided to make Oklahoma her permanent home. Kayla has worked since graduation as an ER nurse at various OKC hospitals but spent the majority of her career with OUMC at the Level One Trauma Center and Adult Emergency Department. She attended the Univeristy of Oklahoma Health Science Center for her masters and graduated in May 2019 with her MSN-Family Nurse Practitioner degree. Kayla has struggled with allergies, asthma, and skin issues for most of her life, but it wasn’t until her daughter was diagnosed with a rare food allergy that she fell in love with the allergy and asthma specialty. She is very grateful to be able to work in a specialty she enjoys and one that has made a positive impact on her life. In her spare time, Kayla loves to spend time with her husband, two daughters, and two dogs. She also loves the travel all over the world and plans to visit all seven continents in her lifetime. She enjoys being active outdoors, especially hiking and backpacking, and does photography as a hobby with her mom. 

Heading photo

Rebekah Green, PA-C

Physician Assistant

Rebekah Green, PA-C was raised in Mustang, Oklahoma and lived in Edmond and Norman before finally settling in Moore, OK. Rebekah discovered her combined passions for patient care and medical research while working in clinical research and as a phlebotomist as she pursued her Bachelor‘s degree from the University of Oklahoma. She completed an undergraduate research internship through OUHSC and coauthored the article, Role of the Skp1 prolyl-hydroxylation/glycosylation pathway in oxygen dependent submerged development of Dictyostelium during her sophomore year of college. After completing a B.S. in Biomedical Sciences with a minor in Chemistry, she spent a year researching cellular neurobiology at OU, coauthoring the paper, AP180 couples protein retrieval to clathrin-mediated endocytosis of synaptic vesicles. She then continued her education, attaining her Master’s degree from University of Oklahoma Health Sciences Center graduating in 2014 from the Physician Associate Program. After graduation, Rebekah worked in urgent care in the OKC metro before transitioning to allergy and asthma so she could spend more time caring for her patients and working to get to the root of what is keeping them from living life to the fullest. Rebekah is thrilled to be at the Oklahoma Institute of Allergy and Asthma where she is able to simultaneously pursue her passion in continuing clinical research while providing the utmost care and compassion for her patients every day.

Rebekah enjoys swimming, sunshine, cooking, traveling, and spending time with family and friends

Heading photo

Leslie Jump, APRN-CNP

Nurse Practitioner

Jill Frost PA-C was born in Oklahoma City and has enjoyed living in Edmond since her early childhood. She went to Oklahoma State University where she graduated Magna Cum Laude through the Honors College, completing degrees in Psychology, Microbiology and Spanish. She furthered her education at the University of Oklahoma Health Sciences Center where she graduated from the Physician Associate program in 2012.
She has practiced family medicine for the last five years providing compassionate care for both pediatric and adult patients. She became interested in working in an area with a focus on asthma and allergies as a result of seeing an increasing number of her patients suffering from these conditions and having a reduced quality of life. She is very excited to join the team at the Oklahoma Institute of Allergy, Asthma & Immunology to provide excellent compassionate care to her patients.Jill resides in Edmond with her husband and son. She enjoys running and doing anything outdoors, traveling, cooking, cheering on her Oklahoma State Cowboys, reading and spending time with family and friends. She also loves volunteering with the Lifekids team at Lifechurch.