Ingredients & materials
This hub holds plain-language explainers for the ingredients, metals and materials behind hypoallergenic claims. Each one reports what its sources say and where they say nothing.
Metals form the largest group. See sterling silver, platinum, niobium, palladium, titanium grades and 316L steel. For nickel itself, there is nickel allergy and jewelry, the EU nickel rules and spot tests. Coatings and metal content are covered in rhodium plating and 14k gold.
Beyond metals are textile and bedding explainers such as OEKO-TEX STANDARD 100, thread count and wool, plus PPD in hair dye.
Each explainer states its source type and its unknowns, so a page that finds little says so rather than filling the gap. None of them names a product, and none treats the word hypoallergenic as a promise.
Three picks to start with
Is sterling silver 925 hypoallergenic?
No source we read says sterling silver is hypoallergenic. US rules say "sterling" means at least 925/1,000ths pure silver, and they set no rule on the remaining alloy metals we could find. Nickel allergy studies report reactions to some silver-plated and nickel-silver items, so the stamp alone does not settle it.
Is platinum jewelry hypoallergenic?
No source we read calls platinum hypoallergenic, and the term has no legal definition. One patch-test study found only 2 positives to a platinum salt in 446 patients, and DermNet lists pure platinum among metals that may be free of nickel. Authors of that study still say platinum jewelry may occasionally cause contact dermatitis, and a "platinum" item can be an alloy.
Surgical steel, 316L and 304: what the grades mean
316L is a specific stainless steel grade; the sources we read give its nickel content as 10 to 14 wt% and do not define "surgical steel". A 1994 lab study found low nickel release from 304 and 316L and much more from 303, but other work shows release depends on the item, not the name.
How we check products in this category
These are explainers, not product lists, and they name no products. Each states what its sources say, labels the study type, and flags what was not found. 'Hypoallergenic' has no legal definition, so none of these pages treats the word as a promise. We read documents and have not tested anything ourselves. The full rules are in the review criteria.
Guides
- Gold karats and nickel: 10k, 14k, 18k
A karat mark says how much of the piece is gold. It does not say what the rest is. DermNet says white gold is usually alloyed with nickel, and its advice for people with nickel allergy is at least 18 karat. Lower karats leave more room for other metals, but no source we read states nickel content for 10k or 14k, so ask the maker. - Asthma and allergy friendly certification: what the program is
The Asthma & Allergy Friendly mark is run by Allergy Standards Limited (ASL), with the Asthma and Allergy Foundation of America (AAFA) as US partner. Independent labs test products against a standard for each product type. The public pages give principles, not numeric limits. - Dust-mite encasements: how pore size works
A 1999 lab study reports mite allergens were blocked below detectable limits by fabrics with an average pore size under 10 micrometres. AAFA says to look for pores too small for mites and their waste to pass. None of the five protector pages we read gave a pore size. - Why dust mites, not feathers, are the usual bedding allergen
The NIEHS and Allergy UK name house dust mites, and proteins in their droppings, as the allergen living in bedding. Two published studies found more mite allergen in synthetic pillows and duvets than in feather ones, so the fill type is not the deciding factor those sources point to. - The EU nickel rule for jewellery, explained
In the EU, nickel in jewellery is restricted by entry 27 of REACH Annex XVII, with release limits of 0.2 and 0.5 micrograms per square centimetre per week. It is EU law. In the documents read, the CPSC says no mandatory US federal requirements exist specifically for jewelry. - Gold plated vs gold filled vs vermeil
In the FTC Jewelry Guides, "gold filled" refers to a mechanically applied gold alloy layer of at least 1/20th of the article by weight, "gold plated" to a thinner surface layer, and "vermeil" to gold over a sterling silver base. None of these terms tells you the metal under the gold is free of nickel. - Is niobium hypoallergenic?
A general reference work calls niobium "physiologically inert and hypoallergenic" and a nickel alternative in jewellery. We found no patch-test or jewellery study on niobium itself, and "hypoallergenic" has no federal definition in the US, so treat the word as a claim, not an assurance. - Is platinum jewelry hypoallergenic?
No source we read calls platinum hypoallergenic, and the term has no legal definition. One patch-test study found only 2 positives to a platinum salt in 446 patients, and DermNet lists pure platinum among metals that may be free of nickel. Authors of that study still say platinum jewelry may occasionally cause contact dermatitis, and a "platinum" item can be an alloy. - Is sterling silver 925 hypoallergenic?
No source we read says sterling silver is hypoallergenic. US rules say "sterling" means at least 925/1,000ths pure silver, and they set no rule on the remaining alloy metals we could find. Nickel allergy studies report reactions to some silver-plated and nickel-silver items, so the stamp alone does not settle it. - Is wool bedding hypoallergenic?
"Hypoallergenic" has no legal definition, and the sources we read do not certify wool as one. Three Australian and New Zealand studies found more dust mite allergen on or in wool bedding. Lanolin contact allergy is a separate patch-test finding, and wool itch is a third thing. - Nickel allergy and jewelry
DermNet describes nickel allergy as one of the most common causes of contact allergic dermatitis, usually long-lasting, with earlobes, wrists and the lower abdomen the typical sites. Diagnosis is by patch test with a clinician. The EU sets numeric nickel release limits for jewelry; a label such as "nickel-free" is the maker's wording. - How nickel release is tested (and the spot test kits)
Labs measure how much nickel an item releases over time, and the EU sets limits in micrograms per square centimetre per week. A home dimethylglyoxime spot test only gives a yes or no on the surface. A 2010 study found it caught 59.3% of the cases the lab method flagged. - What does OEKO-TEX STANDARD 100 mean?
OEKO-TEX describes STANDARD 100 as a label for textiles tested against a list of over 1,000 harmful substances, with stricter limits where skin contact is more intense. The pages read say nothing about allergy outcomes or dust mites. - Palladium in white gold: what to know
DermNet says white gold is usually alloyed with nickel, with palladium-based alloys as an alternative. Palladium can cause contact allergy too. In a 2000 study it always occurred with nickel sensitivity, and a 2019 Spanish study found 91.8% of palladium-sensitised patients were also nickel-sensitised. - Pillow fill types compared
No source we read ranks down, feather, polyester, foam, latex, wool or buckwheat for allergy. The one direct fill comparison found more mite allergen on synthetic than feather pillows after a year, so the cover and washing routine matter as much as the fill. - PVD coating on jewelry
PVD (physical vapor deposition) puts a thin film, such as titanium nitride, on a metal. Two jewelry makers say their PVD finish sits on titanium. The sources we read give no wear life for jewelry coatings, and one EU rule requires a coating to hold a nickel limit for two years of normal use. - Rhodium plating and skin reactions
Rhodium is a thin coating, not the metal underneath. DermNet says the plating on white gold protects against nickel at first but eventually wears off over months or years, leaving the alloy against skin. Rhodium can itself cause contact allergy, but the sources read show only rare cases. - Thread count and allergies
We found no standard, regulator page or study that links a sheet's thread count to allergy outcomes. The mite-barrier research we read measures pore size and material type (woven, non-woven, coated), and one lab study found an ordinary cotton sheet let mite allergen through. - Titanium for jewelry: grades and "implant-grade" explained
The jewelry makers we read name ASTM F-67 (described by one as pure, unalloyed titanium) or F-136 (described as implant grade). "Implant-grade" alone names no standard. We could not open ASTM or ISO pages, so we do not state what F-136 or ISO 5832-3 specify. - What is PPD in hair dye?
PPD is a chemical widely used in permanent hair dye. DermNet says a partly oxidised form of it can cause contact allergy, and dermatology abstracts say a related dye ingredient, toluene-2,5-diamine, is also a common sensitiser that often cross-reacts with it. Allergy diagnosis is a clinician matter. - Surgical steel, 316L and 304: what the grades mean
316L is a specific stainless steel grade; the sources we read give its nickel content as 10 to 14 wt% and do not define "surgical steel". A 1994 lab study found low nickel release from 304 and 316L and much more from 303, but other work shows release depends on the item, not the name. - Why jewelry turns skin green
A 2019 dermatology review lists exogenous copper among the causes of greenish skin staining, and copper is among the most common metals in jewelry. Reviews describe copper as a very weak sensitiser, so green skin alone is not evidence of an allergy; itching, redness or a rash is a separate matter for a clinician. - Why drug-labelled products are not on this site
This site never recommends or ranks a product that carries a drug claim or drug labelling (an SPF or sun-protection claim, a Drug Facts panel, a claimed antibacterial or antiperspirant active). The FDA says such products follow drug rules and labelling. Our rule is editorial, not a legal requirement.