European Standard Battery Allergen number 19.

Nickel(II)sulphate.

#patchtest #dermtwitter #medtwitter #MedEd #contactdermatitis #octothorpe #IronMan

Nickel is the most common contact allergen in the world. It is the core of most patch test questions outside of dermatology and some within. Let's start with a basic question.

A 27F has allergic contact dermatitis to her earrings. She patch tests positive to nickel and the earrings leech nickel on DMG testing. Where would they most likely be from?

The correct answer is Brazil. Being such a common allergen, nickel has been restricted in release from the "Nickel Directive" within the EU. 0.2ug/cm2/week for piercing material and 0.5ug/cm2/week for other metalic objects worn next to skin is the maximum according to REACH regs.

Brazil is the only country outside of the EU in that list. Added to which, at the last World Congress of Dermatology in Milan, the main nickel allergy stories were coming from Brazil.

With the REACH (Restriction, Evaluation, Authorisation and Restriction of CHemicals) regulations, you would think nickel allergy would be a thing of the past. However, it turns up in many places you would not expect. More of that later.

Nickel is a transition metal. It is too small by itself to be recognised by the immune system but being a transition metal, it is a Lewis acid. So it accepts electron pairs easily from amino and carboxyl groups on our proteins and easily forms complexes.

Transition elements have partially filled d orbitals making them ideal for being picked up by the ligands of our immune system and have absorption often in the visible spectrum in solution, giving them colour. Remember copper(II)sulphate?

Which is why metals are sometimes used in cosmetic pigments and tattoo inks. Sometimes the shine of eyeshadow could be metallic fragments.

Now a more tricky question. A 34M has finger tip dermatitis which is better when on holiday. He works in the hospital canteen in Wales. Patch testing shows nickel allergy (++ reaction D2 and D4). What is the most likely source?

The REACH regulations apply to materials held close to skin. Cutlery would be stainless steel so would not release nickel. Scourers are mostly plastic but even then, automated washing is utilised in most canteens. Till buttons are plastic.

The correct answer is coins

About 10 years ago, the Royal Mint who produce coins in the UK, changed the composition of coins to have more nickel. As coins are not worn next to the skin, they do not have to abide by the REACH regulations. However, frequent contact also caused dermatitis.

This is less of a problem now as many payments are contactless through cards, phones and watches. Even so called copper coins leach a lot of nickel. You can detect this with a cotton swab soaked with dimethylglyoxime. It turns pink in the presence on nickel.

Patch testing to metals like dichromate, cobalt and nickel can have false positives often in people with atopy. These are actually irritant reactions due to the inherent barrier compromise in atopy. So if you see all three positive, it could be false. Especially is atopic.

I believe it was Graham Johnston who called this 'The Atopic Triad'

Management is identification of the source of the nickel and removing it from the environment. Often, people with nickel allergy do not find a source of their allergy and we put it down as "unknown relevance".

People with nickel allergy are often also allergic to palladium as they cross react. This may have implications if you have dental work, work with jewellery or are Tony Stark. #IronMan should have seen a patch tester.

Finally, being a patch tester has some awesome moments. A colleague from another speciality came to see me because of a rash on his face at the temples and brow.
I took a second then took off his glasses and applied dimethylglyoxime.

The frame was negative. Of course it was. It followed REACH regulations. The screws holding the frame together almost glowed pink.
Needless to say, he was impressed. We have some good days in patch.

So that's nickel allergy. Rarely used for colours in cosmetics but possible. Don't forget coins and sunglasses screws. Thanks for reading.

Whoops, forgot to tag @patchtestYu and @DrStevenTChen for the inspiration