Nickel allergy is a contact allergy (also referred to as type IV or delayed type hypersensitivity). Unlike immediate hypersensitivities (such as pollen, insect venom and most food allergies), the reaction in delayed type hypersensitivity occurs some time after exposure. Following contact with the allergen, it can take 24 to 72 hours before the first symptoms appear. This ‘delay’ is caused by what are called helper T cells (medical term: T-lymphocytes).
Helper T cells play an important role in the immune system and are found in the lymph nodes and inner layers of the skin. Their function is to protect against certain infections. They attach to foreign substances and activate other cells in the immune system so that they destroy the foreign substances. The so-called memory T cells are then formed. These are cells that have remembered precisely which invaders are unwanted so that they can react faster in the event of re-exposure.
In a contact allergy, the helper T cells remember a presumably harmless substance like nickel. If the skin is then re-exposed to the environmental substance, the helper T cells transform in the upper skin layers and cause an inflammatory reaction. The time delay also occurs because the cells need to travel along this path.
Prevalence of Nickel Allergy in Children and Adults
Nickel is the most common contact allergen in the world. There are a number of studies that have determined how many people have developed a sensitivity (allergic disposition) to nickel based on skin tests. For Germany, a study that analysed the data of more than 100,000 patients between 2005 and 2014 revealed that an average of 8.5% of children from birth to tens years, 12.35 % of adolescents between 13 and 17 years, and 15.5% of adults have a nickel sensitivity. By way of comparison, a Europe-wide study has shown that sensitisation has occurred in 25.9% of the population in Italy, 24% in Spain and 11.9% in Denmark. While sensitisation does not mean that all of those who tested positive experience allergy symptoms, it is clear that sensitisation is a condition for the manifestation of an allergy. In other words: the more sensitised people there are in a given country, the greater the chances are that they will develop contact eczema. As it turns out, women are generally at higher risk of developing a nickel allergy than men. This is due in part to the fact that contact with costume jewellery and body piercings promotes nickel sensitisation.
True symptoms in the form of allergic eczema – triggered by nickel or other substances – develop in 8.0% of German adults over the course of their lifetime. This was revealed in an extensive patient survey conducted by the Robert Koch Institute between 2008 and 2011 in which 12.7% of women in Germany indicated that they had once received a ‘contact allergy’ diagnosis. For men, the figure was 3.4%. For children, 5.6% had contact eczema.
The word ‘eczema’ comes from the Greek and literally means ‘to flare up/boil up’. In most patients, symptoms occur only on the areas of the skin that came into contact with the allergen (for instance, the skin surface around the navel from an allergy to a nickel-containing belt buckle or trouser button). Common nickel contact points are the palms of the hands, fingers, navel, ears and wrists. Typical symptoms of a nickel allergy are intense itching, burning or pain, redness, swelling, papules, weeping blisters at the contact site, and peeling or thickening of the skin in the case of chronic contact.
Nickel is virtually everywhere. The metal is found in jewellery, wristwatches, batteries, piercing jewellery, euro coins, eyewear, prosthetic joints, espresso machines, irons, office supplies, paper, tattoo inks, potting soil, door handles, dental braces, cigarette smoke, musical instruments, flatware, umbrellas, leather goods, hypodermic needles, hairpins, hair curlers, cooking pots and mobile phones. In the 1930s, garters and knitting needles were common allergy triggers; since the 1970s, jeans buttons, costume jewellery and piercing jewellery have been the main the offenders. Occupational nickel allergies also occur in people who work as cleaners or at cash registers.
The EU nickel directive stipulates that nickel-containing products intended for direct and prolonged contact with the skin may release no more than 0.5 µg Ni/cm2/week. For post assemblies inserted into piercings, the rate of nickel release is restricted to no more than 0.2 µg/cm²/week. The release of nickel from toys is also restricted by the EU REACH regulation to 0.5 μg/cm2/week.
Besides industrially manufactured products, foods such as potatoes, grains and fruit also contain nickel, since the metal is taken up during the growth process.
An important step in the diagnostic procedure is the patient history. The doctor asks the patient about his or her habits, family predispositions and symptoms, and deduces the potential causes from this information. Sometimes it can be difficult to tell contact allergies apart from other forms of eczema, such as atopic dermatitis. A skin test can be useful in the diagnostic process.
If nickel is a suspected allergy trigger, the findings from the patient history are further investigated with a skin test. A patch test is used to diagnose a contact allergy. For this test, adhesive tape with test chambers is applied onto the skin, usually on the back. The test chambers contain allergens and, if necessary, other suspected substances. The test results are read after 48 and 72 hours.
Contact allergies can be triggered by various substances. Besides nickel, substances such as cobalt, chromate, preservatives, plant-based and synthetic perfumes, lanolin alcohol, Balsam of Peru and dyes can also cause allergic inflammatory processes in the skin. In order to avoid further contact with the allergen, it is important to identify the allergy-triggering substance as precisely as possible.
The most effective method for relieving symptoms is to avoid the allergy-triggering substance. People who are allergic to nickel should stay away from everyday objects containing nickel and avoid prolonged skin contact. If contact cannot be avoided completely, safety measures such as gloves or protective clothing can help.
If eczema persists despite strict allergen avoidance, cortisone creams can be used to relieve the symptoms.
In rare cases, the nickel content in food can exacerbate eczema in patients with a severe nickel allergy. But before putting such patients on a low nickel diet, a doctor should perform an oral provocation test with nickel. The thresholds and trigger foods vary by individual, and patients should therefore seek the help of a nutrition specialist in order to determine which foods are safe and which need to be avoided.
Research is currently underway to investigate immunotherapy options for nickel allergy.
Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016