Nickel allergy

De Janice Joneja discusses its diagnosis and management

nickel-allergyIn nickel-sensitive people, a rash called contact dermatitis develops where the nickel has been in contact with the skin or mucous membrane for a period of time.(1) The reaction often occurs when the nickel-sensitive person is in direct contact with nickel-containing items such as jewelry, metal studs, watchbands, belt buckles, thimbles, and other metal-containing objects. The reaction is known as a cell-mediated delayed hypersensitivity (type IV hypersensitivity) reaction. Contact with the nickel induces local T-cell lymphocytes to produce cytotoxic cytokines that cause the itching, reddening, and scaling typical of dermatitis.(2)

Nickel related food allergy was first suspected when dermatologists noticed that some people had outbreaks of dermatitis on skin that had not been in contact with any known allergens. They suspected that the allergen might be something that these people had eaten and so looked for sources of known contact allergens, such as nickel, in commonly eaten foods.(3) Nickel occurs naturally in many foods and can also be introduced into the food during processing – from metal cooking utensils or containers, for example (4).

Dermatitis, especially on the hands, may develop as a secondary response to nickel sensitisation and the rash may later spread to other body surfaces. This may be a reaction to nickel in foods in those who were initially sensitised by direct skin contact with nickel. (5) Cases of erythema multiforme (6) and vasculitis (7) have also been occasionally reported after eating nickel-containing food.

Diagnosis of Nickel Allergy

As with any contact allergy, diagnosis is by a patch test. The nickel allergen (usually in the form of nickel sulphate) within the patch is placed on the skin and left in place for up to 72 hours. The area under the patch is usually observed after 48 hours. Because type IV hypersensitivity is a delayed response, the reaction may take 2 to 3 days to become visible. In a positive reaction, the area of skin under the patch will turn red and possibly itch and blister if the reaction is severe.

Dermatitis triggered by nickel in food is usually suspected when a chronic dermatitis persists without obvious contact with nickel-containing objects. Elimination and challenge is at present the only method to identify this cause of the reaction. A low-nickel diet is followed for a period of 4 weeks. If the rash subsides, a challenge with foods with high nickel content will usually indicate that ingested nickel is a trigger for the reaction. (8-11)

The level of nickel in foods

Because all foods contain some level of nickel, a nickel-free diet is not possible. However, some foods are much higher in their nickel content than others.

Levels can vary according to the variety of the plant species or the nickel content of the soil in which the plant was grown or, in the case of seafood, of the aquatic environment. In addition, different laboratories employ a variety of tests to detect nickel in food, so frequently data from one source can disagree markedly with that from another. In most studies, the richest sources of dietary nickel are found in nuts, dried peas and beans, whole grains, and chocolate.

In addition, processing a food can increase its nickel content. For example, minute traces of nickel from metal grinders used in milling flour can increase the nickel in flour considerably, and stainless-steel cookware will increase the level of nickel in the food cooked in it.

As a result it is difficult to get an accurate picture of nickel levels in most foods.. A comprehensive table of nickel levels in foods can be found in Reference (11) below. In addition, there a number of internet sites that provide information, for example, the lists for Penn State Hershey Medical Center or the Melisa Foundation

Nickel and Iron
Most ingested nickel remains unabsorbed and is excreted in the feces. Usually less than 10% of the nickel in food is absorbed (6) but this amount increases in people with iron-deficiencies and lactating mothers. Nickel and iron use the same transport system to cross the intestinal mucosa, so if iron is being transported, nickel is excluded. Accordingly, individuals who are sensitive to nickel should include iron-rich foods in their diet.

Nickel Contact Dermatitis and Oral Tolerance
The most common cause of nickel dermatitis is direct contact with nickel-containing objects. People who have tested positive for nickel using a patch test (on the skin of the forearm or back) should avoid contact with all objects containing the metal.

However an increasing number of studies are now suggesting that oral exposure to nickel may help to  reduce the severity of  dermatitis caused by direct contact with related to nickel or even prevent it. (12,13) According to other studies, oral exposure to nickel can worsen established nickel contact dermatitis initially, but prolonged exposure can reduce the clinical symptoms. (14)

But the subject of nickel-contact dermatitis, nickel allergy, and achievement of tolerance is confusing from a practical point of view because of the extremely complex series of events that occur in the immune system. Nickel contact dermatitis is part of a cell-mediated (type IV) hypersensitivity reaction; nickel allergy is possibly an IgE-mediated (type I) hypersensitivity (15) and the precise mechanism that allows the immune system to achieve tolerance, especially to foods, is unclear at present.

Management of allergy to ingested nickel

Clinical studies suggest that some nickel-sensitive people benefit from avoiding foods with high amounts of nickel. However, opinions differ on what constitutes a nickel-restricted diet. In one research study, an oral dose of nickel (as nickel sulfate) as low as 0.6 mg produced a positive reaction in some nickel-sensitive people. (16) Another report indicated that 2.5 mg was required to induce a flare-up. (17) Because the levels of nickel required to induce a reaction have varied widely in different studies, it is difficult to determine a ‘safe level’ of dietary nickel for nickel-sensitive people.

However, dietary nickel often is not the sole cause of the dermatitis. In these cases, avoiding nickel in the diet may improve the situation but does not entirely eradicate the symptoms. If symptoms have resolved on the diet, challenge with foods with high nickel content should lead to a flare-up of skin reactions if a person is indeed allergic to dietary nickel.


  1. Schram SE, Warshaw EM, Laumann A. Nickel hypersensitivity: a clinical review and call to action. Int J Dermatol. 2010;49(2):115-125.
  2. Walsh ML, Smith VH, King CM. Type 1 and type IV hypersensitivity to nickel. Australas J Dermatol. 2010;51(4):285-286.
  3. Veien N. Dietary treatment of nickel dermatitis. Acta Dermatol Venereol. 1985;65:138-142.
  4. Nijhawan RI, Molenda M, Zirwas MJ, Jacob SE. Systemic contact dermatitis. Dermatol Clin. 2009;27(3):355-364, vii.
  5. Christensen OB, Moller H. External and internal exposure to the antigen in the hand eczema of nickel allergy. Contact Dermatitis. 1975;1:136-141.
  6. Friedman SJ, Perry HO. Erythema multiforme associated with contact dermatitis. Con­tact Dermatitis. 1985;12:21-23.
  7. Hjorth N. Nickel dermatitis. Contact Dermatitis. 1976;2:356-357.
  8. Booth J. Nickel in the diet and its role in allergic dermatitis. J Hum Nutr Diet. 1990;3:233-243.
  9. Han HJ, Lee BH, Park CW, Lee CH, Kang YS. A study of nickel content in Korean foods. Korean J Dermatol. 2005;43:593-598.
  10. Jorhem l, Sundström B. Levels of lead, cadmium, zinc, copper, nickel, chromium, man­ganese, and cobalt in foods on the Swedish market, 1983–1990. J Food Compost Anal. 1993;6:233-241.
  11. Joneja, JV.  Nickel Allergy, Chapter 22. The Health Professional’s Guide to Food Allergies and Intolerances.  Academy of Nutrition and Dietetics. 2013: 215-222
  12. Ysart G, Miller P, Crews H, et al. Dietary exposure estimates of 30 elements from the UK Total Diet Study. Food Addit Contam. 1999;16(9):391-403.
  13. Morris DL. Intradermal testing and sublingual desensitization for nickel. Cutis. 1998;61(3):129-132.
  14. Panzani RC, Schiavino D, Nucera E, et al. Oral hyposensitization to nickel allergy: pre­liminary clinical results. Int Arch Allergy Immunol. 1995;107(1-3):251-254.
  15. Santucci B, Cristaudo A, Canmistraci C, Picardo M. Nickel sensitivity: effects of pro­longed oral intake of the element. Contact Dermatitis. 1988;19:202-205.
  16. Estlander T, Kanerva L, Tupsela O, Keskinen H, Jolanski R. Immediate and delayed al­lergy to nickel with contact urticaria, rhinitis, asthma and contact dermatitis. Clin Exper Allergy. 1993;23:306-310.
  17. Cronin E, de Michiel A, Brown SS. Oral nickel challenge in nickel-sensitive women with hand eczema. Ann Clin Lab Sci. 1981;11:91.
  18. Veiein NK, Menne T. Nickel contact allergy and a nickel-restricted diet. Semin Dermatol. 1990;9(3):197-205.

Additional Resources
For client education material on nickel allergy and other food allergies and intolerances, look for Food Allergies and Intolerances: Client Education Tools for Dietary Action / Tools for Dietary Management

You can buy all of Dr Joneja's books here in the UK or here in the US.

First published February 2014

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