What is the primary cause of contact dermatitis?

Contact dermatitis is primarily caused by exposure to allergens or irritants. This skin condition occurs when the skin comes into direct contact with substances that provoke an inflammatory response. Allergens can include materials like nickel, certain preservatives, or fragrances, while irritants may consist of harsh chemicals, soaps, or detergents that damage the skin's protective barrier. The immune response triggered by these foreign substances leads to symptoms such as redness, swelling, itching, and blistering.

Other options like excessive moisture, genetic factors, and environmental pollutants can contribute to skin issues but are not the main cause of contact dermatitis. Excessive moisture can lead to other skin conditions like intertrigo or fungal infections. Genetic factors may influence a person's susceptibility to skin conditions in general but do not directly cause contact dermatitis. Environmental pollutants can have a negative impact on skin health as well but are not specific triggers for contact dermatitis. Thus, the direct role of allergens or irritants is critical in defining this skin condition.