Camphor
In plain terms
A strong-smelling compound, once distilled from camphor-tree wood and now mostly made synthetically, used in medicated rubs and balms for its cooling, counter-irritant feel. It is the classic smell of vapor chest rubs.
What the evidence shows
Camphor is the counter-irritant in vapor rubs and muscle balms, and its safety turns entirely on dose, age, and whether it is swallowed. On adult skin, at the concentrations the FDA allows in over-the-counter products, it works as a topical analgesic and the agency lists it as safe and effective for that use; the same monograph caps how much a product may contain and bans the old concentrated camphorated-oil preparations that caused poisonings. The hazard is that camphor passes readily through skin and the gut and is neurotoxic in quantity: swallowing even a small amount can bring on seizures in a young child within an hour, and case reports describe exactly that after a toddler took a household balm. Children carry the highest camphor risk, from accidental ingestion to over-application on broken skin, which is why pediatric groups warn against these products for infants and toddlers. For an adult using a capped, labeled product on intact skin as directed, camphor is a reasonable topical; the conditions that make it dangerous are ingestion, young children, and heavy use on damaged skin.
On the label
Listed as camphor among the active ingredients, often in a Drug Facts box since it is regulated as a topical drug. Keep camphor and menthol rubs away from infants and toddlers, and never apply to broken skin or take internally.