Forest in a bottle: scented oils may boost immunity after cancer treatment
NCT ID NCT05012813
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study tested whether breathing in humidified wood or fragrant oils could mimic the immune-boosting effects of a forest walk. 28 adults who finished chemotherapy or radiation for early-stage breast or prostate cancer took part. The goal was to see if this approach is practical and to measure changes in natural killer cells, which help fight infections and cancer.
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Study facts
What this study's own registry entry says, in plain language.
- Phase
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Not a phased trial
Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
- Participants
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28 people
The number who actually took part.
- Started
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Jul 2022
- Finished
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Mar 2025
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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18 years and older
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
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Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * Age \>= 18 years. Both men and women and members of all races and ethnic groups will be included * Participants must have histologically or cytologically confirmed breast cancer or prostate cancer (hormone therapy excepted) who are in stage I-V with or without evidence of metastasis using the Cancer Therapy Evaluation Program (CTEP) Simplified Disease Classification * Participants must be within 12 months of their first diagnosis of breast or prostate cancer * Criteria for solid tumors: Participants must have measurable disease, per doctor of medicine (MD) and data in medical record * Participants must have no history of autoimmune disease * Ability to understand and the willingness to sign a written informed consent document Exclusion Criteria: * If they have asthma. Rationale: forest oils may be a possible trigger for asthma * If they have a known allergy to citrus peel or pine forests. Rationale: forest oils may cause contact dermatitis and coughing * If they are unable to detect common odors from commercial fragrances. Rationale, forest oils are humidified as an aroma to be inhaled in the simulate the forest greenspace immersion (SFIT) * First diagnosis of breast or prostate cancer is longer than 12 months ago. Rationale, NK cell number recovery may be complete by this time after first treatment * Febrile illness/infection within previous two weeks. Rationale, immune biomarkers will reflect previous febrile illness * Current tobacco or tobacco use within 1 hour of start of SFIT. Rationale: forest oils may cause contact dermatitis and coughing * Prior autoimmune disease, are on immune-modulating therapies (endocrine therapy allowed). Rationale, because of their poor prognosis rather than being in early stages of cancer * Had surgery or invasive procedure in the past two months. Rationale, because of their poor prognosis rather than being in early stages of cancer * Inability to complete study requisites
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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OHSU Knight Cancer Institute
Portland, Oregon, 97239, United States
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