This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Dermatitis, Subject name: Dental
Most common precipitant of contact dermatitis is - 
Select and explain. 
A. Gold, B. Nickel, C. Silver, D. Iron
B: Nickel
Answer: B: Nickel 
Explanation: nickel is the most common sensitisers all over the world. the prevelance of nickel sensitivity varies from 4-13%. nickel produces allergic contact dermatitis. clinical presentation: exudative eczema, nummular eczema or dry lichenified eczema. lesions appear beneath earrings, bracelets, bangles, hairpins, rings, wrist watches,safetypins, buttons, stethoscopes. IADVL textbook of dermatology, contact dermatitis page 559