Metal allergies and sensitive skin

Fifty small discs

In a hospital dermatology department, someone is sitting very still while a row of small discs, each about a centimetre across, is taped to their back. Each disc holds a different substance, about fifty of them in all: metals, perfumes, rubber chemicals, preservatives. A pen marks where each one sits. Then they go home in an old shirt, under instructions not to get their back wet for the week. A cool, shallow bath, the leaflet allows, is fine.

This is patch testing, and it is how a suspected metal allergy is confirmed. It is slow, a little inconvenient and, for anyone who has spent months wondering why their earlobes itch, enormously useful. By the end of the week, the skin has given its answer.

What a metal allergy is

Doctors call a rash caused by something touching the skin contact dermatitis. Dermatitis is another word for eczema, meaning inflamed skin. The NHS and the British Association of Dermatologists describe two kinds.

• Irritant contact dermatitis. The substance damages the outer layer of the skin directly. Soaps, detergents, solvents and frequent contact with water are the usual causes, and according to the NHS this is the more common kind.
• Allergic contact dermatitis. The immune system reacts to one particular substance, called an allergen. Some metals, especially nickel, are among the best known causes.

An allergy takes two meetings. The NHS explains that the first contact sensitises the body without any visible reaction. It is only on later contact that the immune system responds and the skin becomes red and itchy. That is why a reaction can start with something that has been worn before without trouble. Once the skin has become sensitive, it will react again each time it meets that allergen.

The American Academy of Dermatology calls nickel one of the most common causes of allergic contact dermatitis, and estimates that more than 18 percent of people in North America are allergic to it, including 11 million children in the US.

What it looks like

According to the NHS, contact dermatitis makes the skin itchy, blistered, dry and cracked. On lighter skin it looks red. On darker skin it can look dark brown, purple or grey. The reaction usually appears within a few hours or days of contact, which is part of what makes the cause hard to spot.

With jewellery, the rash usually shows up where the metal touches. The American Academy of Dermatology names earrings, earring backs and watches as some of the biggest culprits, though necklaces, rings and bracelets can do it too. Away from the jewellery box, belt buckles, bra hooks, jeans studs and zips commonly contain nickel too.

Not every rash where jewellery sits is an allergy. Irritant dermatitis, from soap, detergents or water, can look much the same: the British Association of Dermatologists notes that the two can feel and look similar. That is one reason doctors use patch testing to find the exact cause.

Nickel, cobalt, chromium and gold

Nickel isn't the only metal that patch testing looks for. The British Society for Cutaneous Allergy, whose leaflets explain each allergen to people after a positive patch test, lists where each one turns up.

Leather has its own rule. Under REACH as it applies in Great Britain, leather articles that touch the skin can't be sold if they contain 3 mg/kg or more of chromium VI, the form that causes the problems.

Gold is the surprise on the list, and the least straightforward. DermNet, a dermatology reference written and edited by doctors, describes gold allergy as most often diagnosed in women, and notes that people with it often react to nickel and cobalt too. It also warns that a positive gold patch test frequently doesn't explain the rash that led to the test. If gold comes up, a dermatologist will tell you what it means for you.

How patch testing works

Patch testing is done in a specialist dermatology department, often after a GP referral. The NHS says a GP may refer you if the cause can't be found, or if your symptoms aren't responding to treatment. The British Association of Dermatologists describes what happens.

• Three visits in about a week. Times vary a little between hospitals.
• Visit one. The substances are taped to your back in small discs or square chambers, about 1 cm across, and the positions marked with ink. Most adults are tested for the 50 or so most common allergens, which include metals. Allow up to two hours.
• Visit two, after 48 hours. The patches come off and any reactions are noted.
• Visit three. Your back is checked again, because allergic reactions can take a few days to show, and the results are explained.

A positive result is a red or pink, itchy, often raised patch where a substance sat, and it usually fades within a few days. A negative result is useful too: it makes an allergy less likely to be the cause. Patch tests don't detect food allergies.

What you can try

Every official source comes back to one idea: find the cause, then keep it off your skin. The NHS says that if you can avoid it, the skin should improve and may clear completely.

• Think about long contact, not every touch. The British Society for Cutaneous Allergy says contact for more than a few minutes is needed for nickel or cobalt dermatitis to come back, so focus on things that stay against your skin: earrings, watches, rings, bracelets and clothing fasteners.
• Choose the metal carefully. The American Academy of Dermatology suggests jewellery that is nickel free or hypoallergenic, or made of surgical-grade stainless steel, 18, 22 or 24 karat yellow gold, sterling silver or platinum. Its advice for watches is a leather, cloth or plastic strap, though for anyone allergic to chromium, the British Society for Cutaneous Allergy says vegetable-tanned leather is fine to wear.
• Test what you already own. Kits that use a chemical called dimethylglyoxime can show whether an object contains nickel, according to the British Society for Cutaneous Allergy.
• Cover fasteners. For metal buttons, zips and snaps on clothing, the American Academy of Dermatology suggests plastic replacements, or a coat of clear nail polish as a barrier, reapplied often.
• Look after the skin. The NHS recommends rinsing off an allergen with warm water and an emollient as soon as possible, and using emollients often and generously to keep the skin hydrated.

The law helps as well. In the UK and the EU, jewellery meant to sit against the skin can't release more than 0.5 micrograms of nickel per square centimetre per week, and posts that go into a piercing are held to a stricter 0.2. A coating doesn't get round the rule: it has to keep nickel release under the limit for at least two years of normal use. The British Society for Cutaneous Allergy advises extra care with things bought outside the EU, where some allergens may not be banned.

When to see someone

The NHS sets out a clear order of help.

• A pharmacist if contact dermatitis is troubling you. They can recommend treatments such as emollients.
• Your GP if your symptoms are persistent, keep coming back, or are severe. They can try to find the cause, suggest treatment, and refer you to a dermatologist for patch testing if needed.
• Urgent advice, from 111 or 111 online, if you have a severe reaction or think the skin may be infected. Signs of infection include symptoms getting rapidly worse, discharge from the skin, increasing pain, feeling generally unwell, or feeling hot, cold or shivery.

The American Academy of Dermatology gives similar advice: see a dermatologist if you think you have an allergy, or if a rash blisters, becomes infected, or comes and goes.

A known metal allergy is also worth mentioning before surgery or dental work. The British Society for Cutaneous Allergy notes that joint replacements, fixing plates and dental products can contain nickel, cobalt or chromium, and that many people with these allergies have no problems with them, but it advises talking to your surgeon or dentist first.

The third visit

Back in the dermatology department, at the end of that long week of shallow baths, the dermatologist reads the skin one last time. Perhaps one small square, the nickel, has turned pink. Perhaps nothing has, and the search moves on to soap or water. Either way, the person walks out knowing what to keep off their skin, and that, more than any label on a box, is what makes jewellery comfortable to wear again.