Acetaminophen is a widely used analgesic and antipyretic.
Uncommon in non-aspirin sensitive patients.
Specific acetaminophen allergy is probably exceptional.
Clinical manifestations
Urticaria (61% of reactions), angioedema, maculopapular exanthemas, fixed drug eruption, pigmentary purpura, exfoliative dermatitis, pruritus, acute generalized exanthematous pustulosis.
Anaphylactic shock.
Diagnostic methods
Cutaneous testing
Skin prick-tests: one positive case reported following generalized urticaria.
Patch-tests: paracetamol syrup in pet. (30%) ; paracetamol suppository in pet. (30%), pure paracetamol powder in pet. (30%): positive in 3 patients with delayed manifestations.
Specific IgE: one case reported following generalized urticaria.
Oral challenge (50 mg, 100 mg, 250 mg, 500 mg, 750 mg) at 30 minute intervals.
Acetaminophen possesses a weak cycloxygenase inhibitor action.
Aspirin-sensitive patients may react to high doses (> 650 mg) of acetaminophen, which suggests cycloxygenase inhibition.
Type I hypersensitivity to paracetamol is rare, but does exist.
Cross reactivity between acetaminophen and other NSAIDs is conflictual (0 to 34%).
Low frequency has been reported when acetaminophen challenge doses of 650 mg or less are administered (0 to 6 %).
Avoid high doses of acetaminophen (>1000 mg) in aspirin-sensitive asthmatic patients.
Use oral provocation challenge to ascertain that analgesic substitutes are safe.
One case of aseptic pustular eruption due to paracetamol with worsening of lesions, (appearance of toxic epidermal necrolysis) and severe hemodynamic disturbances following intravenous use of propacetamol hydrochloride.


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