Allergic contact dermatitis
Last Updated: 2023-07-07
Author(s): Anzengruber F., Navarini A.
Contact dermatitis, contact allergy
Type IV allergy mediated by sensitised T lymphocytes on contact exposure to triggering allergens. In some cases, an airborne contact may be causative.
- Prevalence in the population between 5-30% (depending on source)
- Women > men
- Acute allergic contact dermatitis
- Chronic allergic contact dermatitis
Within 1-2 days, a erythematous plaque forms at the site of the contact allergen, which is initially limited to the actual site of contact. Afterwards, satellite lesions form and the border is blurred. The plaque is infiltrated and vesicles are formed. Depending on the intensity, this effect can also be dramatic with large-scale blisters, erosions at the opening, crusts and superinfection.
Because this is a T cell reaction, which can persist for some time without antigen replenishment, removal of the contact allergen is not immediately diagnostic. On the contrary, the reaction may continue (see also drug exanthema) before it improves (crescendo).
Since we observe a spreading with persistent contact, the clinical picture resembles a generalised disease with time, but the focus still remains on the contact site.
- Epicutaneous testing
Depends on the allergens in question as well as the scattering patterns.
In some cases, performing a ROAT (repeated open application test) can be helpful.
Analysis of ingredients and avoidance of sensitive preparations (wool wax) is useful.
If allergen exposure persists and/or additional eczema-maintaining factors such as irritant influences occur, the eczema may become chronic.
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