Isocyanate MDI

Code: k76
Allergen: Isocyanate MDI conjugated to a human serum albumin (HSA) carrier.
 
Certain protein allergens and chemicals capable of acting as haptens occur at high concentrations in workplace environments. They represent a significant sensitization risk also for less atopic individuals due to their often high concentration in the air.

Allergen Exposure

Isocyanates are widely used in the production of polyurethane plastics, glues and paints. Individuals at risk are polyurethane foam makers, upholsterers, spray painters, wire coating workers, plastic molders, rubber workers, fabric coaters, metal rod coaters, truck body insulators and persons applying artificial turf and others.
 
Unexpected exposure
Isocyanates have been mentioned in relation to the Sick Building Syndrome.
 
Environment
Any workplace where isocyanates are used in significant amounts.

Potential Cross-Reactivity

The three isocyanates (TDI, MDI and HDI) are closely related structurally being HSA-conjugated haptens and there is some allergenic crossreactivity (1). However, the major specificity depends on the type of isocyanate exposure.

Clinical Experience

IgE-mediated reactions
A wide spectrum of potentially allergic respiratory symptoms have been described and up to 5% of exposed workers have been reported to have developed asthma at work (2). IgE antibodies to isocyanates have been found in 14-19% of sensitised workers (1, 3).
 
Other reactions
Non-immunological, irritative mechanisms are likely to be of importance.

References

  1. Baur X: Immunologic cross-reactivity between different albumin-bound isocyanates. J Allergy Clin Immunol 1983, 71, 197-205.
  2. Butcher BT, Karr RM, O’Neil CE, Wilson MR, Dharmarajan V, Salvaggio JE, Weill H: Inhalation challenge and pharmacologic studies of toluene di-isocyanate(TDI)-sensitive workers. J Allergy Clin Immunol 1979, 64, 146-152.
  3. Butcher BT, O’Neil CE, Reed MA, Salvaggio JE: Radioallergosorbent testing of toluene di-isocyanate-reactive individuals using p-tolyl isocyanate antigen. J Allergy Clin Immunl 1980, 66, 213-216.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.