Whereas the presence of nickel in certain objects coming into direct and prolonged contact with the skin may cause sensitization of humans to nickel and may lead to allergic reactions; whereas for these reasons the use of nickel in such objects should be limited.
The above sentence is very complicated. Please provide me a simplified synonymous version consisting of multiple sentences:
The presence of nickel in certain objects that come into direct and prolonged contact with the skin can cause sensitivity to nickel in humans and lead to allergic reactions . Therefore , the use of nickel in such items should be limited .