Formaldehyde


The simple formaldehyde molecule is a highly sensitizing molecule that is the underlying cause of contact dermatitis in many patients. Exposure to formaldehyde gas at work and in the home (insulation with urea-formol foam) can lead to the development of asthma.
 
It is also used for sterilization, notably of dialyzers, as an antibiotic additive in grooming products (toothpaste, shampoo, soaps) and in certain medications (antihepatitis B vaccine, certain allergoids).
 
Incidence
Anaphylactic shock is uncommon (hemodialysis and dentistry). Contact dermatitis is frequent.
 
Risk factors
Previous exposure to formaldehyde.
 
Clinical manifestations
Differentiate from irritation syndrome (ocular, nasal, bronchial).
 
General: anaphylactic shock.
 
Cutaneous: urticaria, angioedema, contact dermatitis, polymorphous erythema, maculopapular rash on the face and in the mouth (dentistry).
 
Respiratory: bronchospasm.
 
E.N.T.: rhinorrhea.
 
Diagnostic methods
 Cutaneous testing.
  • prick-tests using formaldehyde solutions at 0.1 and 1% are often positive in subjects presenting immediate reactions. Results should be read immediately (20 minutes).
     
  • patch-tests using a formaldehyde solution at 1% are often positive in subjects with contact dermatitis (high doses are irritating and should not be used).
Specific IgE antibodies against formaldehyde can often be detected by RAST or ELISA in subjects with immediate manifestations.
 
Mechanisms
IgE-mediated hypersensitivity (anaphylactic shock).
 
Cell-mediated hypersensitivity (contact dermatitis).
 
Type III: IgG antibodies against formaldehyde/serum albumin conjugates have been detected in patients exposed through the respiratory or parenteral route.
 
Management
Avoid using dialysis membranes sterilized with formaldehyde in patients with previous allergic skin reactions to formaldehyde.
 
Perform an intradermal test with antihepatitis B vaccine in patients presenting contact dermatitis to formaldehyde (risk of generalized urticaria or eczema).

References

  1. Wantke F, Hemmer W, Haglmuller T, Gotz M, Jarisch R, "Anaphylaxis after dental treatment with a formaldehyde-containing tooth-filling material", Allergy, 1995; 50 (3): 274-6 
  2. Bousquet J, Michel F.B, " Allergy to formaldehyde and ethyleneoxide", Clin. Rev. Allergy, 1991; 9: 357-70. 
  3. Bardana E.J Jr, Montanaro A, "Formaldehyde: an analysis of its respiratory, cutaneous and immunologic effects", Ann. Allergy., 1991; 66 (6): 441-52 
  4. Maurice F, Rivory J.P, Larsson P, Bousquet J, "Anaphylactic shock caused by formaldehyde in a patient undergoing long term hemodialysis", J. Allergy Clin. Immunol., 1986; 77 (4): 594-7.

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