A mild acid valued in scalp care for clearing dead surface skin, scale, and oil. Its link to hair is indirect, with no recognized way to grow new hair. Its strongest support is clearing scalp scaling, which may reduce shedding tied to a treatable scalp condition. Inexpensive and generally well tolerated, with mild irritation the main drawback. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Serum salicylate | Undetectable / negligible | Detect systemic absorption with heavy or high-concentration use |
| Ferritin (iron stores) | 50–70 ng/mL | Identify iron deficiency as a treatable shedding cause unrelated to salicylic acid |
| Renal function (eGFR) | >90 mL/min/1.73 m² | Reduced clearance raises salicylate accumulation risk with heavy use |
Cadence: Reassess scalp scaling and tolerance at roughly 2–4 weeks, then periodically every 1–3 months