Extract and Oil
Rosemary oil (Rosmarinus officinalis) and lavender oil are common ingredients in “hair/scalp” products, often promoted for soothing the scalp, improving hair appearance, or supporting hair growth. Rosemary oil has been studied in androgenetic alopecia; one randomized comparative trial reported that topical rosemary oil performed similarly to 2% minoxidil over six months. Separately, rosemary extracts have shown 5-alpha-reductase–related activity in experimental settings, which is one reason rosemary appears in “DHT-friendly” hair formulations—though lab findings don’t always translate directly to meaningful whole-body hormone effects in humans from topical use. Lavender oil is more often discussed in relation to endocrine signaling: a NEJM case series described prepubertal gynecomastia associated with repeated topical exposure to lavender/tea tree products that improved after stopping, and in-vitro work has suggested weak estrogenic and anti-androgenic activity for certain components, while later reviews argue human evidence remains limited and not definitive.
In PFS/PSSD/PAS discussions, these oils come up because they sit near pathways many people feel sensitive to: rosemary is discussed in a “DHT/androgen-pathway adjacent” way, and lavender is discussed in a “hormone receptor activity” way. Even if many people tolerate these ingredients, sensitized individuals sometimes report flares after introducing concentrated oils or using them repeatedly, particularly when multiple hair-loss actives are stacked together. Community risk cues often include higher concentration products, frequent application, leave-on formulations, and using oils alongside other androgen-modulating hair treatments (ketoconazole, saw palmetto blends, minoxidil, etc.).
(1) https://pubmed.ncbi.nlm.nih.gov/25842469/
(2) https://www.nejm.org/doi/full/10.1056/NEJMoa064725
Crash Anecdotes (Community Reports):
How to Interpret This Page
This page summarizes anecdotal reports and community observations, not medical evidence. “Risk” here refers to how frequently severe or prolonged symptom worsening is reported, not to proven causation or population-wide probability. Individual responses vary widely, and absence of issues in some users does not rule out significant reactions in others.
Risk Signal Based on User Reports
Reports of Mostly Transient Flares, Higher Variance With Concentrated Oils (for PFS/PSSD/PAS):
Among individuals who already have PFS/PSSD/PAS, rosemary and lavender oils/extracts are occasionally mentioned in community reports as preceding symptom flares. Concerns typically focus on hormone-adjacent signaling (rosemary in a DHT/5-alpha-reductase context; lavender in an endocrine receptor-activity context) and on the fact that essential oils can deliver concentrated bioactive compounds through repeated topical exposure. Many reports describe effects that improve after stopping, but some individuals describe longer-lasting destabilization, especially with frequent use of concentrated oils or leave-on scalp products.
For individuals without these conditions, rosemary and lavender oils are widely used in cosmetics and are generally tolerated, though sensitivity reactions and endocrine concerns have been raised in specific contexts (particularly repeated exposure in case reports). Given the variability in products and individual responses, some people with PFS/PSSD/PAS choose to avoid concentrated essential oils during stabilization, or test cautiously—one change at a time—and discontinue if a clear, consistent worsening occurs.
Evidence basis: Limited clinical hair-loss trial data for rosemary; mechanistic/in-vitro endocrine findings for lavender; case reports; anecdotal reports (online forums, self-reports); no controlled studies examining PFS/PSSD/PAS-specific outcomes.
