Patch testing with tulipalin A
In our clinic, tulipalin A is normally tested with tulipalin
A in pet. (0.01%) (Chemotechnique) and tulipalin A in
aq. (0.01%) (Aldrich Chemie). Both materials gave good
results, although tulipalin A in aq. gave rather strong
reactions. Thus, a lower test concentration (0.005% aq.)
was chosen for this field work. Unfortunately this concentration
still resulted in some strong reactions. Although
there were some strong reactions, there were no real
problems in drawing conclusions about sensitization.
Three superficial, bullous reactions without any erythema
were regarded as toxic. We have noticed this patch test
effect before in persons who worked during patch testing
in humid and hot conditions. An extra contributing factor
is the selective high pressure of the test chamber on the
back skin due to the bending posture during work.
A problem was the preparation of tulipalin A in pet. It
gave good results in the limited amount of people who
were tested with it in the clinic. However, in this study the
results were far too weak. Only four persons had a 1 +
reaction and there were no 2 + or 3 + reactions. This
raises questions about stability and bioavailability of
tulipalin A in pet.
The comparison of the patch tests results with the
probability of sensitization on the basis of the history and
the dermatologic examination showed that a total of 15
workers (31.3%) were misinterpreted (eight false positives
and seven false negatives). This leads to the conclusion
that a history alone is not satisfactory for
determining sensitization for a material in populationbased
studies. This is in accordance with the common
dermatologic knowledge that it is generally not possible to
distinguish allergic and irritant contact dermatitis on the
basis of history and clinical picture.