Cobalt allergy often goes hand-in-hand with nickel allergy. The two metals, which sit alongside one another on the periodic table of elements, can be found in similar products, meaning avoiding prolonged exposure to one overlaps strongly with what you need to do to avoid exposure to the other. So where there is nickel — everyday metal objects, such as zips, coins, keys, scissors, cheap jewellery — there may well be cobalt.
Along with chromium, cobalt is the next main metallic allergen after nickel, and was the third metal to be named ‘Allergen of the Year’ by the American Contact Dermatitis Society, in 2016.
Cobalt allergy typically presents with itchy or red or angry rash at the site of exposure, which can take a long time to clear. This is a contact allergy — allergic contact dermatitis — a delayed hypersensitivity reaction through the skin.
As it is tested for on all main contact dermatitis testing panels, it will be diagnosed if you undergo patch testing.
Like nickel, it can be found in trace amounts in cosmetics such as mineral make-up and hair dye as a contaminant.
Unlike nickel, whose salts and compounds are not permitted for use in cosmetics, one cobalt compound — cobalt aluminium oxide (CI 77346) — is allowed in Europe (but not in America). It is a green colour, sometimes used in nail polish, for instance.
You’ve probably heard of ‘cobalt blue’, as cobalt compounds lend their deep blue hues to a number of pigments, used in clothing, textiles, pottery, paints, inks and other deeply coloured materials.
They are also very commonly found in tattoo inks, and those who wish to have a tattoo may well have to seek out a tattooist who uses inks not derived from the cobalt salts. There are some artificial non-metallic blue dyes out there, such as CI 69800 (Pigment Blue 60) or CI 74160 (Pigment Blue 15). Or else you may wish to avoid blue/green shades altogether.
Cobalt in Food
Vitamin B12 contains a cobalt atom and so cobalt is considered an ‘essential’ mineral on that basis. Dietary exposure to B12 is not problematic for those with cobalt allergy, but if you require a vitamin B12 injection for medical reasons, you may experience a reaction. Speak to your doctors in this instance.
Where a low-nickel diet may be indicated for those with nickel allergy, a low-cobalt diet is far less likely to be recommended, although sometimes is for dyshidrotic eczema. This requires proper and rigorous medical support and should not be undertaken without guidance. There are tools, such as the Cobalt Companion, which users can turn to for support.
Cobalt in Leather
Reactions to leathers — such as behind the legs from sitting on leather sofas — is more commonly associated with chromium.
However, research has relatively recently shown that it is also be present to reactive degrees in some leathers, and may be a cause of some contact dermatitis symptoms in those with cobalt (but not chromium) allergy.
My book, The Metal Allergy Guide, has much more on cobalt allergy, including the low-cobalt diet, and other advice on how to avoid cobalt exposure.