2. What impact do chemicals have on the skin?

The skin is the second route of contact with toxic substances. Skin irritation accounts for some 60-80% of contact dermatitis observed in clinical practice.

Skin disorders are characterized by erythema (redness) and edema (swelling). The application of a chemical substance that penetrates the stratum corneum can cause damage to the underlying layers of keratinocytes, activating a cascade of events that results in skin irritation. Mediators at the origin of the inflammatory cascade are secreted by damaged keratinocytes, and act in particular on stromal and endothelial cells of the dermis. The dilation and increased permeability of endothelial cells are responsible for the erythema and edema observed.

Strong inflammatory reactions can evolve into vesicles, desquamation (peeling) and thickening of the epidermis (hyperkeratosis).