Acute-stage eczematous reaction
Acute contact dermatitis is characterized by a largely uniform metachronous sequence of pathological symptoms over the entire lesion.
Mild form: erythema at the site of exposure to the toxin, contact traces, and itching are possible.
Severe form: ranging from vesicular papules (histologically: spongiotic blisters) to blisters, usually causing strong itching. A feeling of tightness of the skin and even pain may occur. Blister rupture is followed by weeping, scab formation, and later by scaliness, generally culminating in restitutio ad integrum. Spreading reactions are possible in the case of an allergic trigger.
Acute irritant contact dermatitis is characterized by: rapid onset (within hours) following generally easy-to-identify exposure, rapid clinical course, and usually also rapid resolution; its monomorphic and often highly intensive clinical symptoms (including possible skin necrosis); subjective symptoms perceived more as burning pain than itching; and clearly demarcated borders around the area of contact and the absence of spreading.
Chronic dermatitis
Chronicity occurs when the skin continues to be exposed to the toxin, thereby preventing spontaneous healing of the dermatitis, or when the dermatitis persists even in the absence of the toxin.
From a morphological perspective, there are eczematous plaques with focal emphasis in more exudative or scalier areas. The initially relatively sharp demarcation becomes increasingly indistinct. The skin has a thickened appearance due to the infiltration of inflammatory cells and skin folds become accentuated (lichenification). The clinical picture is increasingly dominated by hyperkeratoses, rhagades, and lichenification.
The onset of chronic degenerative contact dermatitis is first seen after exposure lasting in some cases for up to years. The initial symptom is generally uncomfortable dryness of the skin, followed by erythema and flaking. Thereafter, it is characterized by a dry, hyperkeratotic-scaly, fissured/rhagade-like lesion of a less exudative nature. It follows a slow clinical course and heals only in a delayed manner, is largely — but not exclusively — restricted to the area of contact, and does not show a tendency to spread.