Our Providers


Our Physicians


Ryan Buckley, MD

Dr. Buckley joined Colorado Allergy and Asthma Centers in 2020. He is board certified by the American Board of Internal Medicine and the American Board of Allergy and Immunology. Dr. Buckley received his Bachelor of Science degree in Physiology with a Chemistry minor from the University of Arizona, graduating magna cum laude. He obtained his... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Kara Crosby, DO

Dr. Kara Crosby joined Colorado Allergy and Asthma Centers in 2018. She is board certified by the American Board of Allergy and Immunology. Dr. Crosby received her bachelor’s degree in biology from Ohio University and completed her medical school education at Lake Erie College of Osteopathic Medicine. She trained in pediatrics at Akron Children’s Hospital... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Mark A. Ebadi, MD

Dr. Mark Ebadi joined Colorado Allergy and Asthma Centers in 2003. He is board certified by the American Board of Allergy and Immunology. Dr. Ebadi received his bachelor’s degree and doctor of medicine from the University of Nebraska. Following his undergraduate education, he was awarded a research fellowship at Dartmouth. He completed internal medicine residency... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Shaila U. Gogate, MD

Dr. Shaila Gogate joined Colorado Allergy & Asthma Centers in 2014. She is board certified by the American board of Allergy & Immunology. Dr. Gogate received her bachelor’s degree in Chemistry from Colgate University in Hamilton, NY. She finished her medical school education at Chicago Medical School and her internal medicine residency at Washington University,... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Leon S. Greos, MD

Dr. Leon Greos joined Colorado Allergy and Asthma Centers in 1993. He is certified by the American Board of Allergy and Immunology. Dr. Greos emphasizes prevention of allergy symptoms through identification of triggers, patient education and rational use of preventive medicine. Dr. Greos received his bachelor’s degree from Amherst College and doctor of medicine from... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Andrea L. Jones, MD

Dr. Jones joined Colorado Allergy and Asthma Centers in 2016. She is board certified by the American Board of Allergy and Immunology and the American Board of Pediatrics. She completed a fellowship in Allergy and Clinical Immunology at National Jewish Health in Denver, Colorado. She is an active member of the Colorado Allergy and Asthma... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Erin E. Kempe, DO

Dr. Erin Kempe joined Colorado Allergy and Asthma Centers in 2016. She is board certified by the American Board of Allergy and Immunology. Dr. Kempe received her bachelor’s degree in Biology from Temple University in Philadelphia, PA. She completed medical school at the Lake Erie College of Osteopathic Medicine in Erie, PA. She then moved... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Jerald W. Koepke, MD

Dr. Jerald Koepke has been practicing medicine in Denver since 1980 when he joined Dr. John Selner at the Allergy Respiratory Institute. On January 1, 1997, the Colorado Allergy and Asthma Clinic merged with the Allergy Respiratory Institute to create Colorado Allergy and Asthma Centers. Dr. Koepke was excited about the blending of these two... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Nan Laoprasert, MD

Dr. Nan Laoprasert joined Colorado Allergy and Asthma Centers in March of 2003. She is a partner and medical director of Colorado Allergy and Asthma Centers. Dr. Nan is certified by the American Board of Allergy and Immunology. Dr. Nan received her Doctor of Medicine from Chiang Mai University in Thailand. She did residency training... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Ross I. Palis, MD

Dr. Ross Palis joined Colorado Allergy and Asthma Centers in 2020. He is board certified by the American Board of Allergy and Immunology. Dr. Palis received his bachelor’s degree from Duke University and his medical degree from Vanderbilt University. He completed his Internal Medicine residency at Barnes-Jewish Hospital/Washington University and his Allergy and Immunology fellowship... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

David S. Pearlman, MD

Dr. Pearlman is a retired founder of Colorado Allergy & Asthma Centers®. Dr. David Pearlman founded Colorado Allergy and Asthma Centers with Drs. Avner and Buckley in 1972. He is certified by the American Board of Allergy and Immunology, for which he also served on the Board of Directors. He is certified by the American... Read more »

Read Full Bio>>

Monica B. Reddy, MD

Dr. Reddy joined Colorado Allergy & Asthma centers in 2016. She is board certified by the American Board of Allergy and Immunology and the American Board of Pediatrics. Her passion is clinical medicine. She believes that the foundation of the doctor and patient relationship is effective communication. She works with her patients to formulate an... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Katherine Tsai, MD

Dr. Katherine Tsai joined Colorado Allergy and Asthma Centers in July 2009. She is board certified by the American Board of Allergy and Immunology. Dr. Tsai received her bachelor’s degree from University of California Irvine and Doctor of Medicine from Washington University in St. Louis School of Medicine. Internship and residency training was completed at... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Our Advanced Practice Providers


Heidi K. Bailey, PA-C

Heidi Bailey received her Bachelor of Arts in Human Biology at the University of Northern Colorado. She received both her Physician Assistant/Child Health Associate Certificate and Master’s Degree from the University of Colorado Health Science Center. Heidi worked in medical research and development. Heidi has enjoyed working in allergy since 2007. She is an allied... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Jessica Gustafson, PA-C

Jessica received her Bachelor of Science in Microbiology from the University of Iowa.  She received both her Physician Assistant/Child Health Associate Certificate and Master’s Degree from the University of Colorado Health Science Center.  She has enjoyed working in the specialty of allergy and asthma since 2007.  She has been involved with multiple clinical research trials... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Kelly M. Hersh, FNP-BC

Kelly received her Bachelors of Science in Nursing from Bradley University in Peoria, Illinois. After working as a registered nurse in several different specialties, she received her Masters of Science degree for family nurse practitioner from the University of Portland in Portland, Oregon. Since joining our practice in 2008, Kelly has enjoyed helping both adult... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Alicia M. McCown, PA-C

Alicia received her Bachelor’s degree from the University of Nebraska – Lincoln. She completed her Master’s of Medical Science and Physician Assistant’s degree from Saint Louis University in Missouri, then relocated to Denver in 2006. Alicia is a member of the American Academy of Physician Assistants and the Colorado Association of Physician Assistants. Physician Assistants... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Nicole A. Mezo, PA-C

Ms. Mezo received her undergraduate degree from Colorado State University, where she majored in Exercise and Sport Science with a concentration in Sports Medicine and a minor in Anatomy and Neurobiology. She received her Physician Assistant degree from George Washington University in Washington, D.C. and her Master’s degree from the University of Nebraska. Physician Assistants... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Katy E. Pfiffner, FNP-C

Katy joined Colorado Allergy and Asthma Centers after earning her Master of Science in Nursing: Family Nurse Practitioner from the University of Northern Colorado. She received her Bachelor of Science in Nursing degree from The University of Akron in Ohio, and has 12 years of experience caring for a diverse population of patients in a... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Nicole R. Rae, PA-C

Nicole joined Colorado Allergy and Asthma Centers in 2000. She received her bachelors degree from Colorado State University and her Physician Assistant certification from The University of Colorado. It is rewarding for Nicole to work with allergy and asthma patients because with effective medications and education they can lead active, productive lives. Physician Assistants are... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Lacey D. Sanchez, NP-C

Lacey received her Bachelor of Science in Nursing from the University of Northern Colorado in 2005. After working as a Registered Nurse at Poudre Valley Hospital in Fort Collins for six years, she decided to pursue an advanced degree, returning to the University of Northern Colorado where she received her (Master of Science) Family Nurse... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Heather Scott, PA-C

Heather attended the University of Colorado Denver, where she received her Bachelor of Science in Biology.  She then received her Master of Medical Science and Master of Public Health degrees from Arcadia University, in Glenside, Pennsylvania.  Heather is a Colorado native and always knew she wanted to return home to serve the community where she... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Martha S. Steffen, PA-C

Martha attended both the University of Northern Colorado and the University of Colorado School of Medicine to earn both her bachelor’s and master’s degrees of Physician Assistant. She graduated in 1985 from the Child Health Associate/Physician Assistant program and has worked with Colorado Allergy and Asthma Centers since then. Physician Assistants are trained to take... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Jennifer M. Toczyski, FNP-C

Jennifer earned her Bachelors of Science in Nursing from University of Louisville. Following graduation, Jennifer spent several years as a travel nurse in hospitals throughout the country specializing in pulmonary and cardiac care. She then served at National Jewish Health, treating and educating patients with allergies, asthma, and immunological deficiencies. After earning her Masters of... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Mona L. Welz, FNP-C

Mona comes to Colorado Allergy & Asthma Centers with over eight years of experience in nursing and leadership. Mona received her Bachelors of Science in Nursing from the College at Saint Benedict, St. John’s University, in St. Joseph, Minnesota. While working as a Registered Nurse at the Mayo Clinic, Rochester and the Childrens Hospital, Colorado,... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Sheila R. Wertz, PA-C

Sheila Wertz received her Bachelors of Arts in Kinesiology from the University of Colorado in Boulder. She received her certificate for Physician Assistant for the University of Colorado School of Medicine in Denver. Since joining Colorado Allergy and Asthma Centers in 2001, she is committed to providing asthma and allergy care to adult and pediatric... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.

Tamara J. Young, PA-C

Tamara received her Bachelor’s in biology from the University of Colorado at Boulder. She received her Physician’s Assistant Certification from the University of Colorado School of Medicine in Denver. Since joining our practice in 1998, Tamara has particularly enjoyed providing as much patient education as possible, with emphasis on asthma prevention and management plans. Physician... Read more »

Read Full Bio>>

This provider can be seen at:

Make an Appt.