IDEA - International Dialogue for the Evaluation of Allergens

Third IDEA Workshop on pre- and prohaptens

20 - 21 October 2015


The third Workshop on pre- and prohaptens (Leuven, October 20 and 21, 2015; Programme) was built on what was discussed and agreed at the June 2015 Expert Workshop on improved mechanistic understanding of pre- and prohapten formation as well as on analytical developments. The intention of this third Workshop was to bridge what has been worked out in the June Expert Workshop and progressed over the summer, with clinical findings.

The objectives of this Workshop were:

  1. To further drive mechanistic understanding of pre- and prohapten formation and to bridge findings with clinical data.
  2. Obtain an agreement on what is known respectively unknown and lay out pathways to close these knowledge gaps.
  3. Work towards solid documentation of current knowledge and its implementation for risk management purposes.

The IDEA Hydroperoxides TF provided an update on the method development and discussed with the participants the remaining activities and next steps. Clinical and experimental data, including cross-reactivity and metabolism processes, was reviewed to get a deeper understanding on the role of prehaptens in contact allergy. Regarding prohaptens, the discussion was focused on the latest scientific and on the methodological challenges to apprehend their formation.

As concluded during the workshop and as reflected in the initial summary for the Rapporteur (Prof. James Bridges), the next steps will be focused on:

  1. The progress of the ongoing research work to deeply understand the role and formation of pre- and prohaptens in the development of contact allergy dermatitis
  2. The inclusion of pre- and prohaptens in the current risk assessment of fragrance sensitizers.


More information is provided in the presentations from the speakers:

Introduction to the Third Workshop on pre- and prohaptens - Speakers: Dr. Hans Bender (Moderator of the IDEA Workshops) and Dr. Matthias Vey (IDEA Management Team)

Hydroperoxide TF report: Update on the work program, status, remaining activities and timelines. Proposals of next steps - Speaker: Dr. Alain Chaintreau (Firmenich)

Prehapten – clinical data and interpretation:
- Update on clinical data - Speaker: Dr. Johanna Brared Christensson (University of Gothenburg, Sweden)
- Discussion on relevance of cross reactivity between fragrance hydroperoxides - Speaker: Prof. Ann-Therese Karlberg (University of Gothenburg, Sweden)
Understanding prohaptens:
- Prohaptens are not a new idea! - Speaker: Dr. David Basketter (DABMED Consultancy)
Pre- and prohapten consideration in current risk assessment (of sensitizers):

Further in the form of smaller working groups the following questions were discussed:

- Group 1: What is needed to integrate pre- and prohaptens in the QRA?
- Group 2: How can we obtain better correlation between dermatological observations and consumer exposure to pre- and prohaptens?


Following an established procedure, a number of key conclusions were derived at the workshop and agreed by all participants. The Rapporteur's Progress Report is now available online.