Cobalt is a silver-coloured metal that gives a blue colour to for example (Chinese) porcelain and glass. Cobalt is a mineral but also occurs naturally in the human body (it is a constituent of B12. The human body therefore contains about 1 to 2 grams of cobalt). Cobalt is also often found in meteorites, together with nickel and iron. Cobalt is generally used for making metal compounds (for example steel pins in bone fractures), metal products such as buckles and tools (for example scissors), magnets and batteries and is therefore often used together with Nickel and Iron. It is an ingredient also often found in cement, hair dye (especially in shades of brown) and in printing ink.
You can recognise Cobalt in the list of ingredients by the symbol Co. Cobalt Chloride or Cobalt Dichloride is a chloride compound of Cobalt (it is pink and powdery) and is therefore often mentioned in the same breath as Cobalt. You can recognise Cobalt Chloride or Cobalt Dichloride in the list of ingredients by the symbol CoCL2.
Cobalt and Cobalt (di)Chloride are known allergens, and are prone to skin allergy, especially when used in combination with Nickel. But beware, an allergy to Cobalt (or Cobalt (di)chloride) alone is rare. Avoiding the substance Cobalt (or Cobalt (di)Chloride) is almost never the solution to a Cobalt allergy. People with a cobalt allergy are usually (in 75% of cases) also allergic to Nickel and/or Chromium (Nickel, Chromium and Cobalt are often used together in the creation of metal compounds). If there is a Cobalt allergy, then there is usually also an allergy to Nickel and/or Chromium. It is precisely these last two raw materials that cause the most complaints in case of an allergy.