Nickel
Nickel is a material belonging to the group of heavy metals.
The material, which is used in the prodution of zippers, buttons and similar textile accessories,
is nowadays not the prefrred choise because of the risks to human health.
Either pure or mixed, nickel might be preferred to make the accessory hard and bright.

EU Law
The importing of nickel-containing products to EU Countries has been restricted since 20th July 2000. In some countries, even prison sentence maybe applicable beginning in October 2001.
Relevant to the issue, below standards are put into practice:
  ΕΝ 1811  Reference test method for release of nickel from products intended to come into directnd prolonged contact with skin.
  ΕΝ 12472  Method for the stimulation of wear and corrosion for the detection of nickel release from coated items.
Nickel releasing criteria for both standards is 0.5mg/cm2/week.

Harms to Consumer Health
Research results show that 2% of men and 10% of women are allergic to nickel.
Accessories, which touch the skin directly and contain nickel, can cause rashes and itching.
Besides countries that are members of EU, lots of other countries prohibit or restrict nickel containing products.