Environmental Causes of Dermatitis.

Environmental, or exogenous, dermatitis is comprised of irritant and allergic contact dermatitis, which account for 80% and 20% of cases of contact dermatitis, respectively. Contact dermatitis is extremely common, and failure to diagnose this entity may result in overlooking a potentially curable driver of disease. In this review, we describe how clinical features, such as morphology or history, can assist in distinguishing exogenous from endogenous causes of dermatitis, and allergic from irritant contact dermatitis. Additionally, we provide an overview of common contact allergens and how dermatitis distribution can suggest possible culprit allergens. Patch testing is needed to confirm contact allergy.