What is a common cause of contact dermatitis?

A common cause of contact dermatitis is indeed allergens or irritants. Contact dermatitis is an inflammatory skin condition that occurs when the skin comes in direct contact with a substance that triggers an adverse reaction. This can include a wide range of materials such as soaps, cosmetics, fragrances, metals (like nickel), certain plants (such as poison ivy), or even fabric detergents.

When the skin is exposed to these substances, it can lead to symptoms such as redness, itching, swelling, and sometimes blistering, depending on the severity and individual sensitivity. The reaction can be immediate or delayed, which highlights the role of the immune system in responding to these irritants or allergens.

While the other options, such as excessive sun exposure, genetic factors, and systemic diseases, can all impact skin health significantly, they do not specifically relate to the localized reactions characteristic of contact dermatitis, which is particularly defined by its direct correlation with external substances. Thus, recognizing allergens and irritants as primary causes is essential in both understanding and managing contact dermatitis effectively.