Isoniazid is a major antituberculosis drug.
5% of patients.
Clinical manifestations
General: fever, flu-like syndrome.
Cutaneous: morbilliform, maculopapular or urticarial rash, contact dermatitis (occupational in nurses and manufactories).
Respiratory: lung infiltrates, interstitial pneumonia.
Diagnostic methods
Cutaneous testing
Intradermal skin-tests: 0.06 to 6 mg/ ml.
Patch-tests: isoniazid 2% in dis. water (contact dermatitis).
Specific IgE.
IgE-mediated hypersensitivity in a few cases.
Delayed hypersensitivity (contact dermatitis).
Desensitization is possible and effective. Start with 0.1 mg and go to 150 mg in 17 hours.


  1. Meseguer J, Sastre A, Malek T, Salvador M.D, "Systemic contact dermatitis from isoniazid", Contact Dermatitis, 1993 ; 28 (2): 110-1
  2. Holland C.L, Malasky C, Ogunkoya A, Bielory L, "Rapid oral desensitization to isoniazid and rifampin", Chest, 1990 ; 98: 1518-9
  3. Asai S, Shimoda T, Hara K, Fujiwara K, "Occupational asthma caused by isonicotinic acid hydrazide (INH) inhalation", J. Allergy Clin. Immunol., 1987 ; 80 (4): 578-82.
  4. Fujiwara K, Saita T, Shimoda T, Asai S, Hara K, "Isonicotinic acid hydrazide as an antigen", J. Allergy. Clin. Immunol., 1987 ; 80 (4): 582-5
  5. Gabrail N, "Severe febrile reaction to isoniazid", Chest, 1987 ; 91: 620-1.

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