Mark T. O'Hollaren, MD
Listed as an allergist, with a practice address in Portland, Oregon.
This record may be out of date. The doctor’s record in the national provider registry hasn’t been updated since 2007, and they don’t appear in current Medicare records. They may have moved or retired. Call before you go.
Practice location 1
511 SW 10th Ave, Suite 1301
Portland, OR 97205
From the records
- Specialty
- Allergist
- Records
- National provider registry only, not updated since 2007. May have moved or retired.
- Registry record
- Last updated July 2007
- NPI
- 1588723787 (national provider registry)
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From CMS’s Doctors and Clinicians file (October 2026) and the national provider registry, NPPES (October 2026). Listings are free and in alphabetical order; we don’t rate or recommend doctors. How we list doctors