Contact allergens provoke allergic reactions by per-cutaneous sensitisation. Most contact allergens are haptens (molecules that have to bind with proteins to be allergising) and induce delayed hypersensitivity reactions, therefore contact eczema. We also note that certain proteins may induce immediate allergic reactions, mediated by the IgE then occurring by contact urticaria, or even more serious reactions generalised some distance from the point of contact (angioneurotic oedema, anaphylactic shock, etc.).
The list of contact allergens inducing contact eczema is very long. The main allergens responsible for delayed hypersensitivity are:
- Metals (nickel, chrome, cobalt…):
Contained in clothing accessories, costume jewellery, the frames of glasses, medical accessories, dyes for paints, paper, ceramics, cements, leathers (tanning with chrome). - Perfumes:
Contained is cosmetic, household and pharmaceutical products. - Drugs:
Corticoids (hydrocortisone and derivatives, 17-butyrate of hydrocortisone and derivatives, budesonide and derivatives), non-steroid anti-inflammatories (ex : ketoprofen, bufexamac). - Balsam of Peru:
Contained in healing products, dental, cosmetic and food products. - Lanolin:
Found in cosmetic products and drug topics. - Preservatives:
- mercury derivatives (ear, eye drops, vaccines),
- methyl isothiazolinone commonly called Kathon CG® (cosmetics, household products, professional oils),
- dibromoglutaronitrile found in Euxyl K 400®,
- formol and formol releasers (toothpaste, varnish, shampoo…),
- parabens,
- hexamidine, chlorhexidine
- Paraphenylenediamine:
Dye in black rubber, lacquers, leathers, textiles, hair dyes, cosmetic products, tattoos with henna. - Epoxy resins:
Plastic industries, flash set glues and adhesives, paints and varnishes.
Among the contact allergens that may trigger contact urticaria, it is possible to mention latex, meat, fish, fruit or vegetables responsible for professional contact urticaria in workers in the agro-food industry, the maggots handled by fishermen.