Allergic reactions to nickel are quite common

Dear Doctor: What can you tell me about an allergy to nickel? I recently had skin testing after experiencing itchy skin, a rash and fluid-filled blisters that several doctors thought might be mosquito-related. Instead, I tested positive for nickel allergy. Even the nickel in my bra clasps and earrings make me break out. Do I need to avoid certain foods? Is this problem hereditary?

Dear Reader: Nickel allergies are quite common. Although nickel is only about .009 percent of the Earth's crust, the metal and its compounds are found in a large number of common objects, such as coins, earrings, rings, watches, bras, belt buckles, mobile phones, medical devices and dental implants. And, as you referenced, nickel is found in small amounts in many foods. Unfortunately, nickel is the most common metal allergy in humans, affecting more than 10 percent of people in the United States. Women are five times more likely to have an allergic reaction to nickel than are men, largely because of their exposure to nickel-containing jewelry.

For people with nickel allergies, nickel ions provoke an immune response within the skin. After multiple exposures, the immune system can overreact when exposed to the metal. This type of reaction is called a delayed hypersensitivity reaction and it occurs 48 to 72 hours after the exposure.

There does appear to be some genetic predisposition to nickel allergies, but really, allergies to nickel are more related to exposure than to heredity. People who frequently handle coins, such as cashiers and toll road collectors, have greater amounts of allergic reactions on the hand than does the general population.

Again, the problem with nickel is how commonly the metal is used in clothing and in jewelry. That can be attributed to its strength and its resistance to oxidation. That said, Denmark has regulated nickel in its consumer goods and thus has the lowest rates of nickel allergy among industrialized countries. Other European countries have taken similar action; the United States has not.

Obviously, the best course of action is to avoid nickel in clothing and jewelry. One way to detect nickel is through a rapid testing kit, or dimethylglyoxime test. Here's how it works: You apply the test solution to a cotton swab, rub the swab on the metal of a product you're thinking of buying and -- if the product contains any nickel -- the swab turns pink.

Titanium, platinum, sterling silver, some types of stainless steel and gold that is at least 18 karats should be free from nickel. As for earrings with nickel (a common metal in such jewelry), you can create a barrier between it and your skin by coating the metal that touches your ear with nail polish or specific products marketed for nickel allergies. For clothing with nickel-containing buttons, you can apply an iron-on cloth over the metal portion or simply use duct tape. Finally, you can use barrier creams on the skin that comes in contact with nickel from jewelry.

Case reports suggest that skin reactions to nickel can diminish with a reduction of nickel in the diet, but your reaction appears to be related specifically to skin contact. So, for you, if you can't avoid nickel, I recommend using a barrier against it.

Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.