At a glance
| Chemical family | Transition metal — pigment, catalyst, and contact allergen |
| CAS number | 7440-48-4 |
| Classification | IARC Group 2B (cobalt metal and soluble cobalt salts — possibly carcinogenic to humans); EU CLP Carc. 1B (H350i — inhalation) for some cobalt salts |
| Where you encounter it | Blue pigments and dyes (cobalt blue, cobalt violet); hard metal alloys (tungsten carbide tools); rechargeable batteries (lithium cobalt oxide); some textile dyes; household dust |
| Sleep micro-environment relevance | Contact allergen in blue-dyed textiles; trace contaminant in household dust. Carcinogenic risk is occupational (inhalation of cobalt metal dust), not from consumer skin contact |
Regulatory & certification status
| European Union | REACH SVHC candidate list (cobalt dichloride, cobalt sulfate, cobalt carbonate, cobalt acetate — all Carc. 1B, Repr. 1B). Authorisation required for industrial use. OEKO-TEX limits extractable cobalt in textiles. Regulatory |
| United States | California Proposition 65 listed (cancer — cobalt and cobalt compounds). OSHA occupational exposure limit: 0.02 mg/m3 (TWA). No consumer-product restriction. Regulatory |
| Canada | CEPA risk assessment identified cobalt-containing substances as priority. Regulatory |
| International | IARC Group 2B (cobalt metal and soluble salts). OEKO-TEX Standard 100 limits extractable cobalt to 1.0-4.0 mg/kg depending on product class. Regulatory |
What it is
Cobalt is an essential trace element (it is the central atom in vitamin B12) and an industrial metal used in alloys, batteries, and pigments. IARC classified cobalt metal and soluble cobalt(II) salts as Group 2B in 2006, based on sufficient evidence of carcinogenicity in animals and inadequate evidence in humans. The EU takes a more precautionary approach, classifying several cobalt salts as Carc. 1B (H350i) via inhalation. The carcinogenic risk is from occupational inhalation of cobalt metal dust, not from dermal contact. Cobalt is also a well-known contact allergen — approximately 1-3% of the general population is sensitised, and cobalt allergy frequently co-occurs with nickel allergy.
Where it shows up in bedding
Cobalt appears in the bedroom primarily through blue pigments and dyes in textiles — blue-coloured sheets, pillowcases, and mattress ticking may contain cobalt-based colourants. For people with cobalt allergy, prolonged skin contact with cobalt-containing dyes can trigger allergic contact dermatitis. Cobalt is also present as a trace contaminant in household dust from outdoor soil and wear of cobalt-containing materials. The amounts are typically very small and not a health concern for non-sensitised individuals.
Citations
- IARC (2006). Cobalt in Hard Metals and Cobalt Sulfate, Gallium Arsenide, Indium Phosphide and Vanadium Pentoxide. IARC Monographs Vol. 86. Source Peer-reviewed
- ATSDR (2004). Toxicological Profile for Cobalt. Agency for Toxic Substances and Disease Registry. Source Regulatory
- ECHA. Cobalt — Substance Information (SVHC candidate). Source Regulatory
Frequently asked questions
Can cobalt in blue sheets cause an allergic reaction?
If you are allergic to cobalt (approximately 1-3% of the population), prolonged skin contact with textiles containing cobalt-based blue dyes could trigger allergic contact dermatitis. Cobalt allergy often co-occurs with nickel allergy. If you experience unexplained rashes from blue or dark-coloured bedding, consult a dermatologist for patch testing.
Is cobalt in textiles a cancer risk?
No. The carcinogenic risk from cobalt is specifically from inhaling cobalt metal dust in occupational settings (hard metal manufacturing, grinding). Skin contact with cobalt in textile dyes does not create inhalable dust and does not pose a carcinogenic risk.
Related compounds
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Last reviewed 2026-07-07. If you find a factual error, contact us.