9-karat gold
On the label: 9k gold · Metal
What it is
37.5 percent gold. Sold as gold in the UK and Europe but below the US minimum of 10k, so it is not marketed as karat gold in the US.
Metals: Solid metals: what the piece is made of all the way through. Purity is written as karat (gold) or parts per thousand (925 silver, 950 platinum).
In the research
No PubMed papers mention this material with jewelry, allergy or eyewear; that is usual for findings and trade terms.
Other metals
Clasp & Lens describes materials from the public record and does not appraise, grade or test pieces; what a listing states is the supplier's statement. If a piece causes a rash, take it off; a reaction that spreads or blisters is a doctor's question, and sunglasses are no substitute for impact-rated eye protection where that is required.