Hypersensitivity reactions to paracetamol (acetaminophen, Tylenol) appear to be increasing

Hypersensitivity reactions to paracetamol (acetaminophen, Tylenol) appear to be increasing, but there are few prevalence data.

This study included 32 patients with suspected paracetamol allergy who underwent skin tests and an oral challenge.

Patients presented with a combination of urticaria, angioedema (face, hands), erythema (cutaneous features in 94%), dyspnea (including laryngeal edema), rhinoconjunctivitis, cough, abdominal pain and anaphylaxis.

Only 2 patients had a positive skin prick test (SPT) and unequivocal history of acute urticaria/facial angioedema/conjunctivitis/cough after paracetamol. One patient had a positive intradermal test.

Oral challenge was positive in 15 of 31 patients (including self-challenge in 4).

Overall, paracetamol hypersensitivity was confirmed in 50% patients.

75% of paracetamol-allergic patients tolerated NSAIDs. 25% were intolerant of NSAIDs.

Specific IgE may be a mechanism underlying paracetamol hypersensitivity in some patients. In 81% of patients, negative skin tests did not exclude paracetamol hypersensitivity, suggesting that it may be mediated by leukotrienes.

The authors suggested that in suspected paracetamol allergy, skin tests should be performed along with oral challenge.

References:

ACAAI protocol for challenge: http://bit.ly/2g6IPv7

Paracetamol Hypersensitivity: Clinical Features, Mechanism and Role of Specific IgE. Rutkowski K, Nasser SM, Ewan PW. Int Arch Allergy Immunol. 2012 May 3;159(1):60-64.
http://goo.gl/zZp9q

Paracetamol (acetaminophen) hypersensitivity - yes, it's real. Annals, December 2000, Volume 85, Issue 6, Pages 508–511, http://bit.ly/2yjn3wm

Selective hypersensitivity reactions to acetaminophen: A 13-case series: SPT was not useful. JACI In Practice http://bit.ly/2i9Jhx8

Comments from Google Plus:

Ahmad Gandour: This study only included 32 we need a larger study ?

Boyan Hadjiev: Better 32 than just case reports. This type of study takes lots of time and energy. The makers of Tylenol would certainly NOT sponsor it (or so I am inclined to believe). I say kudos to the researchers. Still if you look at results, you can't rely on ANY skin tests to predict outcome at all!!! Sounds like oral challenge is the only way, and it was positive in 50% of patients. That's pretty low.