Can you be allergic to lanyards? I am 17 years old and I have eczema, after wearing a lanyard a lot, the back of my neck constantly has eczema on it

Irritation vs allerg. You may have developed a contact dermatitis to a chemical in the lanyard. However the lanyard may also be rubbing against your neck causing irritation and aggravating a common eczema area, the neck. Either way remove the lanyard, use your topical anti inflammatory medication and see if the area clears.