It can also be caused by. 1  chemicals. 2  contact lens wear(https://www.cdc.gov/contactlenses/index.html) (especially wearing lenses overnight) 3  foreign bodies in the eye (like a loose eyelash) 4  indoor and outdoor air pollution caused, for example, by chemical vapors, fumes, smoke, or dust. 5  fungi.
Voluntarism, sometimes referred to as voluntary action, is the principle that individuals are free to choose goals and how to achieve them within the bounds of certain societal and cultural constraints, as opposed to actions that are coerced or predetermined. 1 Volunteerism. 2 Varieties.
Mutualism: Mutualism is a positive reciprocal relationship between two species. Through this relationship both species enhance their survival, growth or fitness. To a certain extent the relationship is more a reciprocal exploitation rather than a cooperative effort on the part of the individuals involved.