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Erica Chen, MD, is a board-certified allergy and immunology specialist practicing at the Allergy and Asthma Specialist Doctors, Inc. location in West Covina, California. Her practice is centered around the treatment of allergic diseases, including nasal allergies and asthma.

Dr. Chen earned her medical degree from the Keck School of Medicine at the University of Southern California. Subsequently, she completed her combined internal medicine pediatric residency and allergy and immunology fellowship training at the Los Angeles County Hospital at the University of Southern California.

Dr. Chen is board certified by the American Board of Allergy and Immunology. She has contributed to multiple peer-reviewed scientific presentations and publications. She also holds numerous professional society memberships, including the American Academy of Allergy Asthma and Immunology and the American College of Allergy, Asthma and Immunology.

Dr. Chen is currently accepting new patients and looks forward to welcoming them to Allergy and Asthma Specialist Doctors, Inc.

Dr. Daniel A. Steigelman, M.D., earned his Bachelor of Science in Bioengineering from the University of California, Berkeley, before receiving his medical degree from the Uniformed Services University of the Health Sciences (USUHS) in Bethesda, Maryland. He completed his post-graduate medical training through the San Antonio Uniformed Services Health Education Consortium (SAUSHEC), where he finished both his residency in Pediatrics and his specialized fellowship in Allergy and Immunology.

Dr. Steigelman is double board-certified, holding credentials as a Diplomate of the American Board of Allergy and Immunology and a Diplomate of the American Board of Pediatrics. These certifications qualify him to diagnose and manage allergic, asthmatic, and immunologic conditions in both children and adults. Alongside his clinical work, he has stayed active in medical education, serving as an Associate Professor of Pediatrics and Medicine at USUHS.

Before transitioning to private practice, Dr. Steigelman spent his career as an active-duty physician in the United States Air Force. During this time, his leadership roles included serving as the Consultant to the USAF Surgeon General for Allergy and Immunology and directing SAUSHEC's Transitional Year residency program. Following his retirement from active duty in April 2026, he joined Allergy and Asthma Specialist Doctors, Inc., providing dedicated care to patients in the Los Angeles community.

POSITIONS

2021 – 2015 Clinical Professor of Medicine

2014 – 2018 Associate Clinical Professor of Medicine

2007 – 1986 Assistant Clinical Professor of Medicine

University of California Irvine, School of Medicine

Division of Allergy and Immunology

101 The City Drive

Orange, CA 92668

HONORS

2021 – 2017 Top Doctors of Orange County, Orange County Medical Association

2021 – 2017 Castle Connolly Top Doctors

2018 – 2017 America's best Physicians, National Consumer Advisory Board 

2017   30 year Recognition Award, Volunteer Clinical Faculty, Division of Allergy and Immunology University of California, Irvine, School of Medicine, American Academy of Allergy, Asthma & Immunology

2015 – 2008 Best Physicians as Chosen by Their Peers, Los Angeles Magazine December

2016 – 2014 Physician of Excellence, Orange County Medical Association

2015 – 2014 Southern California Super Doctors

2013 – 2009 Patients' Choice Award

2015 – 2002 Top Doctors, Doctors Across America, Guide to Top Doctors

Joshua Ang, DO, is a board-certified allergy and immunology specialist dedicated to helping patients at Allergy and Asthma Specialist Doctors, Inc., in Pasadena and West Covina, California. He provides personalized care for a wide range of concerns, including seasonal and environmental allergies, asthma, eczema, food allergies, sinus issues, and immune system conditions.

Dr. Ang earned his medical degree from the Philadelphia College of Osteopathic Medicine and completed his Internal Medicine Residency at Midwestern University – Mountain Vista Medical Center. He then completed his Allergy and Immunology Fellowship at Larkin Community Hospital in Miami, where he served as chief fellow.

Certified by both the American Osteopathic Association for Adult and Pediatric Allergy and Immunology and the American Board of Internal Medicine, Dr. Ang stays current on the latest treatments and research. He is an active member of professional organizations, including the American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma & Immunology.

Dr. Ang is passionate about working closely with his patients to create customized treatment plans that improve quality of life and help them breathe easier every day.

Jean Hanley M.D., FACAAI, is a board-certified allergy, asthma, and immunology specialist at the Allergy and Asthma Treatment Center in Glendale, California. Her practice focus is the treatment of allergic diseases.
Dr. Hanley is a native of Los Angeles and earned her medical degree from the University of California, Los Angeles. Her pediatrics residency was completed at Harbor-UCLA Medical Center followed by a subspecialty fellowship in allergy, asthma, and immunology at Ronald Reagan UCLA Medical Center.

As an allergist at the University of Southern California, she implemented the national Breathmobile Program, a comprehensive, mobile allergy and asthma clinic treating medically-underserved children at their schools within Los Angeles Unified School District and adults at Los Angeles Comprehensive Community Health Centers. She was awarded Physician of the Year by the Allergy and Asthma Foundation of America for her work.

Dr. Hanley is board-certified by the American Board of Allergy and Immunology and is a member of the American College of Allergy, Asthma, and Immunology. She has published extensively in scientific and community journals and has given numerous presentations and television and radio interviews in the field of allergy and asthma on a local and national level.

Marine Demirjian, MD, is a board-certified allergy and immunology specialist at Allergy and Asthma Treatment Center in Glendale, California. Her practice emphasis is centered around the treatment of allergic diseases. 

A native of Los Angeles, Dr. Demirjian earned her medical degree from the University of California, Los Angeles School of Medicine. Subsequently, she completed her internal medicine residency at the Ronald Reagan UCLA Medical Center and allergy-immunology fellowship at the VA Greater Los Angeles Healthcare System and Children's Hospital Los Angeles.

Dr. Demirjian is board certified by the American Board of Allergy and Immunology as well as the American Board of Internal Medicine. She holds numerous professional society memberships, including the American Academy of Allergy Asthma and Immunology, American Contact Dermatitis Society, and the American College of Allergy, Asthma, and Immunology. She also worked an associate clinical instructor of allergy and immunology at UCLA’s Department of Medicine for ten years. 

As an allergy specialist, Dr. Demirjian believes that identifying and eliminating environmental factors is critical to controlling allergic diseases. In addition, with allergy injections, she can help patients achieve tolerance to their allergic triggers so they can live their lives free of allergy symptoms.