**3. Irritant contact dermatitis**

Clinical evidence indicates that a primary, irritative form of contact dermatitis can develop upon a single first contact with chemicals in previously unsensitized patients.

Irritant contact dermatitis (ICD), also known as ''primary ACD'' or ''primary CHS'' develops upon skin exposure to strong haptens such as urushiol, primine, DNFB and DNCB (Kanerva et al., 1994).

ICD is the result of the liberation of proinflammatory mediators upon skin exposed to haptens which in turn promote recruitment from blood of inflammatory cells to tissue sites. The magnitude of ICD is similar to that of classical ACD but presents a different kinetic since the onset of the skin inflammation is delayed in ICD by 5 days, a time period needed to achieve T cell priming.

The eczematous lesions of ICD are morphologically indistinguishable from those present in conventional ACD, suggesting that common mechanisms could be involved in the two

inflamed skin can be investigated by FACS analysis after isolation. In figure 4 we provide a

Clinical evidence indicates that a primary, irritative form of contact dermatitis can develop

Irritant contact dermatitis (ICD), also known as ''primary ACD'' or ''primary CHS'' develops upon skin exposure to strong haptens such as urushiol, primine, DNFB and DNCB

ICD is the result of the liberation of proinflammatory mediators upon skin exposed to haptens which in turn promote recruitment from blood of inflammatory cells to tissue sites. The magnitude of ICD is similar to that of classical ACD but presents a different kinetic since the onset of the skin inflammation is delayed in ICD by 5 days, a time period needed

The eczematous lesions of ICD are morphologically indistinguishable from those present in conventional ACD, suggesting that common mechanisms could be involved in the two

upon a single first contact with chemicals in previously unsensitized patients.

detailed protocol to isolate lymphocytes from skin.

(Kanerva et al., 1994).

to achieve T cell priming.

**3. Irritant contact dermatitis** 

Fig. 2. Allergic contact dermatitis experimental protocol.

processes. Importantly, using an experimental murine model of primary CHS induced by a single DNFB or FITC painting on mice ears without subsequent challenge, Saint-Mezard and colleagues were able to show that the pathophysiology of one-step ICD is identical to that of two-step classical ACD, involving the same effector and down-regulating immune mechanisms (Saint-Mezard et al., 2003). Remarkably, ICD responses were strictly dosedependent and reproducibly more important in C57Bl/6 mice than in BALB mice (Bonneville et al., 2007). More importantly, Bonneville et al. demonstrated an interrelationship between ICD and ACD and showed that upon hapten rechallenge the intensity of ACD reaction is proportional to the magnitude of the former ICD response (Bonneville et al., 2007).
