Pathogenesis (development of disease)
Allergic contact dermatitis is often triggered by irritant (nonallergic) contact dermatitis, that is, by direct damage to the skin. Also, the hyperergic response of the immune system to the substance may be the trigger.
Allergen contact may also be airborne, in the form of so-called aerogenic allergic contact dermatitis, e.g. to phytoallergens.
The hapten (low molecular substance) docks to the carrier of the skin. This complex is recognized by T cells, which then release immune mediators. At the end of this cascade, inflammatory infiltrate occurs. Allergic contact dermatitis is thus a T-cell mediated immunopathologic reaction (is thus not IgE mediated). It is a type IV allergy (synonyms: allergic late type reaction, type IV allergy, “delayed type”). The reaction time is 24-72 hours.
Etiology (Causes)
Exogenous factors
- Exposure to the triggering substance; the following substances are among the most common triggers of allergic contact dermatitis:
- Azo tattoo dyes
- Bufexamac (anti-inflammatory drug for topical treatment of the skin).
- Fragrances – in about 2% can be detected by epicutaneous test (synonyms: patch test, patch test) a contact allergy (here: fragrance allergy); main allergens are: Hydroxyisohexyl-3-cyclohexene carboxaldehyde (HICC), oakmoss (Evernia prunastri), cinnamaldehyde, hydroxycitronella, hexylcinnamaldehyde.
- Epoxy resin
- Formaldehyde
- Potassium dichromate
- Cobalt chloride
- Lanolin (alcohols)
- Mercaptobenzothiazole (vulcanization accelerator in rubber manufacturing for products such as tires and technical rubber articles).
- Sodium thiosulfatoaurate
- Neomycin/neomycin sulfate (antibiotic)
- Nickel (nickel sulfate) [potentially contained in: Jewelry, watch cases and bands, buttons, rivets, buckles, zippers and metal markings, if used in clothing; no claim to completeness!]
- Octocrylene (UV filter) [rather rare]
- Palladium
- Paraben mix (preservatives)
- Peru balsam
- P-phenylenediamine (dyes)
- Propolis (bee product, which is also called bee kite resin).
- Sorbitan sesquioleate (emulsifier in dermatics and cosmetics).
- Turpentine
- Thiram (chemical compound from the group of dithiocarbamates).
- Toluene-2,5-diamine
- 4-tert-butylphenol-formaldehyde resin (PTBFR; adhesive in rubber articles).
- Sensitization potency of the substance
Endogenous factors
- Genetic load: genetic factors, unspecified.
- Ethnicity
- Gender – males to females is 1: 10 (nickel allergy).
- Occupations – hairdressing, metalworking, cleaning companies and catering (hand eczema).
Behavioral causes
- Smoking
- Tattoos (see below exogenous factors).
Disease-related causes
Skin and subcutaneous (L00-L99).
- Concomitant skin diseases, unspecified
Medications
- Medication use, unspecified
Other causes
- Dental crowns (palladium) – in the case of metal contact allergy, exposure to dental crowns with a palladium alloy could play a role.
