A plant oil applied to the skin. It kills bacteria, yeasts and mites by breaking their outer coats, but barely crosses skin, so it has no plausible longevity role. The strongest case is mild-to-moderate acne. Aged oil causes lasting allergy in a small but real fraction of users; swallowing it is dangerous. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Patch test to oxidised tea tree oil 5% | Negative at 48 and 96 hours | Detects sensitisation before a rash spreads |
| Fungal microscopy and culture | Negative at end of course | Confirms fungal cause and clearance |
| Demodex count per eight epilated lashes | Fewer than 5 mites | Tracks mite burden during lid treatment |
| Inflammatory lesion count on the face | ≥50% reduction by week 12 | Primary success measure for acne |
| Probing pocket depth at treated sites | Below 4 mm | Gauges added benefit over deep cleaning |
| Serum estradiol and total testosterone | Age- and sex-appropriate reference range | Only if unexplained breast tissue develops |
| Scalp scaling severity | No established target; clear reduction vs baseline by week 4 | Benchmarks scalp response against trial data |
Cadence: Tolerance at 1 and 4 weeks; efficacy at 12 weeks (skin, scalp) and 3 and 6 months (nail, periodontal). Objective confirmation at end of course only.