I casually browsed a few of them and from what I found is that aromatherapy works for some people mainly in mild cases of anxiety, not for pain relief. Some articles:
* https://onlinelibrary.wiley.com/doi/abs/10.1002/gps.1688
"In summary, lavender is effective as an adjunctive therapy in alleviating agitated behaviours in Chinese patients with dementia."
* https://onlinelibrary.wiley.com/doi/abs/10.1002/gps.473
"Post hoc analysis suggested that at this time of day the AM consistently reduced motor behaviour when compared with CA (p = 0.05). This provides preliminary evidence of a measurable sedative effect of aromatherapy massage on dementia within a robust scientific paradigm."
* https://www.sciencedirect.com/science/article/pii/S152695230...
"Our results suggest that aromatherapy-massage might be an effective intervention for postpartum mothers to improve physical and mental status and to facilitate mother-infant interaction."
* https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2648....
"There were no statistically significant differences in the physiological stress indicators or observed or reported behaviour of patients' ability to cope following any of the three interventions However, those patients who received aromatherapy reported significantly greater improvement in their mood and perceived levels of anxiety They also felt less anxious and more positive immediately following the therapy, although this effect was not sustained or cumulative"
* https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1440-1819....
"These results indicate that in chronic hemodialysis patients hiba oil is an effective, non‐invasive means for the treatment of depression and anxiety, and that lavender alleviates anxiety."
* https://onlinelibrary.wiley.com/doi/abs/10.1002/ptr.26500303...
"Although the overall number of supervening infections and their characteristics were not modified by the treatment, the frequency of relapse at least appears to have been significantly lowered in the group receiving treatment compared to the group receiving placebo."
* https://onlinelibrary.wiley.com/doi/abs/10.1002/smi.1402
"These findings suggest that peppermint aroma may be useful for relieving stress. "
* https://link.springer.com/article/10.1007/s11695-007-9170-7
"Our results suggest that lavender aromatherapy can be used to reduce the demand for opioids in the immediate postoperative period."