Contact Dermatitis, 2001, 45, 21–25
Printed in Denmark . All rights reserved
Copyright C Munksgaard 2001
T. A1, K. E. A2, B. B3, M. B3, P. J. F4, B. G3,
U. H5, B. K6, T. M ´1 J. S5
1Gentofte University Hospital, Denmark,2Odense University Hospital, Denmark;3Malmö
University Hospital, Sweden;4Hautklinik Dortmund, Germany;5Mekos Laboratories AS, Denmark;
6Pharmacia Corporation, Sweden
The preservatives imidazolidinyl urea (IMID, Germall 115) and diazolidinyl urea (DU, Germall
II) are commonly used in cosmetic products and are well-known sensitizers. The aim of the present
study was to establish the optimal patch test concentration in hydrophilic dried-in vehicle (TRUE
Test) for IMID and DU. 181 patients were included in the study. Of these, 150 were patients
referred for patch testing, 12 were patients with known allergy to IMID and 19 were patients with
known allergy to DU. 76 consecutive patients and the 12 IMID-allergic patients were patch tested
with a dilution series IMID (0 to 600 mg/cm2), formaldehyde (180 mg/cm2) and DU (200 mg/cm2).
74 consecutive patients and the 19 DU-allergic patients were patch tested with a dilution series of
DU (0 to 600 mg/cm2), formaldehyde (180 mg/cm) and IMID (200 mg/cm2). A positive dose-response
relationship was found. The number of doubtful reactions decreased with increasing test concen-
trations. No late reactions were observed. A patch test concentration in hydrophilic dried-in vehicle
(TRUE Test) of 600 mg/cm2was found to be adequate and safe for both IMID and DU.
Key words: imidazolidinyl urea; Germall 115; diazolidinyl urea; Germall II; TRUE Test; formalde-
hyde; dose-response; concomitant reaction; allergic contact dermatitis; contact allergy; patch test-
ing technique. C Munksgaard, 2001.
Accepted for publication 2 February 2001
Imidazolidinyl urea (IMID) and diazolidinyl urea
(DU) are preservatives frequently used in cosmetic
products. Both IMID and DU are well-known
sensitizers, and frequent cases of allergic contact
dermatitis reactions to both chemicals have been
reported (1–8). IMID (trade name: Germall 115)
was responsible for 3% of the reactions in a patch
test study of patients with cosmetic reactions (1).
Contact dermatitis reactions to IMID have been
reported occasionally since its introduction in 1970
(2–4). Another member of this chemical group,
DU (trade name: Germall II), was introduced on
a large scale in 1982. Since then several cases of
sensitization have been observed (5–7). Data from
the North American Contact Dermatitis Group
(NACDG) show a response rate of 2.5% to 3.7%
(8). A Swedish multicentre patch test study shows
a response rate of 1.8% to DU (2% aq.) and 1.3%
to IMID (2% aq.) (9) in patients referred for ec-
Both IMID and DU release small amounts of
formaldehyde by hydrolysis in aqueous conditions.
When a positive reaction to a formaldehyde-re-
leasing compound occurs concurrently with a posi-
tive reaction to formaldehyde, the question arises
as to whether the allergic reaction is caused by the
compound itself or by the formaldehyde released.
The literature does not provide a definite answer to
this question, but most data indicate that contact
allergy toward the compounds themselves actually
exists. Concomitant reactions between DU and
IMID have also been reported (10–12). In vitro
skin permeation studies through pig skin indicate
that IMID and DU do possess their own sensitiz-
ing ability, as only very limited amounts of form-
aldehyde permeate the skin (13).
Because of the ability of both IMID and DU to
release formaldehyde upon hydrolysis, it was very
important to choose a patch test vehicle in which
hydrolysis of these compounds is unable to occur.
One of the concepts of TRUE Test is that all the
allergens are incorporated in dry vehicles, and
therefore the optimal vehicles for these compounds
were selected between substances such as polyvi-
done and different celluloses, which are all capable
of making gels that can be dried into thin layers.
Complete stability of both IMID and DU was seen
when the vehicle polyvidone was used. This means
22AGNER ET AL.
that no free formaldehyde is present when the
patch is applied.
The aim of the present study was to establish the
optimal test patch test concentration in a hydro-
philic dried-in vehicle for IMID and DU.
Materials and Methods
181 patients, 65 men and 116 women, were in-
cluded in the study. Patients with widespread der-
matitis were excluded. Patients participated after
written informed consent, and the local ethical
committees have approved the study.
Patients were recruited from dermatological
Dortmund Hautklinik, Germany. Of the 181 pa-
tients included, 150 were consecutive patients re-
ferred for patch testing, 12 were patients with a pre-
Fig. 1. The dose-response relationship for imidazolidinyl urea
and diazolidinyl urea at D3. The number of patients with
doubtful reactions decreased with increased test concentration.
The x-axis is logarithmic.
Fig. 2. (a, b) The degree of response for imidazolidinyl urea at
D3 and D7. The concentrations are given in mg/cm2: 600 in red,
200 in green, 67 in yellow, 22 in blue and 7 mg/cm2in white
vious positive patch test to IMID and 19 were pa-
tients with a previous positive patch test to DU.
Consecutive patients referred for testing were ran-
domized to patch testing with a dilution series of
either IMID or DU in a blinded study design. 76
consecutive patients and the 12 IMID-allergic pa-
tients were patch tested with 6 concentrations of
IMID (TRUE Test: 0, 7, 22, 67, 200, and 600 mg/
cm2), a Finn Chamber with 2% IMID (in aq. or in
pet. depending on the tradition of the patch test
clinic), 1 formaldehyde patch (TRUE Test: 180 mg/
cm2) and 1 DU patch (TRUE Test: 200 mg/cm2). 74
consecutive patients and the 19 DU-allergic pa-
tients were patch tested with: 6 concentrations of
DU (TRUE Test: 0, 7, 22, 67, 200, and 600 mg/cm2),
a Finn Chamber with 2% DU (in aq. or in pet. de-
pending on the tradition of the patch test clinic), 1
formaldehyde patch (TRUE Test: 180 mg/cm2), and
1 IMID patch (TRUE Test: 200 mg/cm2). Test tapes
were produced with patches mounted in 3 different
combinations. For both allergens polyvidone was
used as a vehicle. Patch tests were removed after 2
days, and reactions were evaluated after 3 or 4 days
and after 7 days. A follow-up, in most cases a tele-
phone interview, was performed after 3 weeks.
23STANDARDIZATION OF TRUE TEST PATCHES
Fig. 3. (a, b) The degree of response for diazolidinyl urea at D3
and D7. The concentrations are given in mg/cm2: 600 in red,
200 in green, 67 in yellow, 22 in blue and 7 mg/cm2in white
Difference in response to the varying test con-
centrations was evaluated by the Friedman 2-way
analysis by ranks. P-values ?0.05 were considered
statistically significant. When statistical significant
differences between patches were found multiple
comparison between patches was performed.
The results of patch testing at day (D) 3 and 7 for
IMID and DU are given in Figs. 2 and 3, respec-
tively. A linear dose-response relationship was
found for both IMID and DU (Fig. 1).
Testing with IMID
Of the 12 IMID patients, 2 did not respond to any
of the patches. Of the 76 consecutive patients
patch tested with IMID, 2 patients reacted posi-
tively to IMID (dilution series as well as Finn
Chamber), and were included in the IMID group
in the analysis of the data. 1 patient reacted to
IMID (1π) in Finn Chamber at D7, but not to
any test concentration in the dilution series.
Fig. 4. Concomitant reaction. The distribution of positive re-
Testing with DU
Of the 19 DU patients 3 did not respond to any of
the patches. Of the 74 consecutive patients patch
tested with DU, 1 reacted positively to DU (both
TRUE Test dilution series and Finn Chamber),
and was included in the DU group in the analysis
of the data. None of the consecutive patients had
doubtful reactions to DU in any concentration at
D3. At D7 1 patient had a doubtful reaction to
DU 600 mg/cm2. 1 patient reacted to DU (1π) in
Finn Chamber at D3 and D7, but not to any test
concentration in the dilution series.
For IMID, a statistical significant difference in
response was found between 600 mg/cm2and 7 mg/
cm2as well as 67 mg/cm2(p?0.05) at D3. At D7
24AGNER ET AL.
statistically significant differences in the response
was found for IMID between 600 mg/cm2and 7 mg/
cm2as well as 22 mg/cm2(p?0.05). No statistical
significant differences were found between re-
sponse rate to 200 mg/cm2patches and 600 mg/cm2.
Statistically significant differences in the re-
sponse to different concentration was found for
DU at D3 between 600 mg/cm2and 7 mg/cm2as
well as 22 mg/cm2(p?0.05), and for DU at D7 the
patch with 600 mg/cm2demonstrated significantly
higher response than the 3 lowest concentrations.
Number of doubtful reactions decreased with in-
creasing test concentration.
During testing with IMID 2 patients experi-
enced flare-up of their previous eczema. At follow-
up 3 weeks after patch testing, 10 patients (2
IMID-allergic and 8 DU-allergic) had persisting
local reactions. No late reactions were observed.
The distribution of positive responses to patch
test with IMID, DU and formaldehyde is given in
Fig. 4. Of a total of 23 patients with previous posi-
tive patch tests to either IMID or DU, only 5 did
not react to patch testing with formaldehyde.
Comparison of test concentrations of IMID and
DU varying from 0–600 mg/cm2shows a statisti-
cally significant dose-response relationship. The
number of doubtful reactions was reduced when
test dose was increased (Fig. 1). Although no se-
vere adverse reactions occurred, a flare-up of pre-
vious eczema was seen in a few patients. Late reac-
tions were not seen. Together these data indicate
that 600 mg/cm2was the most advantageous of the
included test concentrations for both IMID and
DU. Doubtful reactions may be interpreted as
either weak positive or irritant reactions. The fact
that the number of doubtful reactions decreased
when test dose was increased, indicates that the
threshold for irritancy was not reached, and that
doubtful reactions in most cases should be read as
a weak positive response (Figs. 2, 3). Theoretically,
the test dose could then be further increased. How-
ever, the sensitivity of the test was found to be suf-
ficient, since an allergic response was reproduced
in 83% and 84% of the IMID and the DU allergic
patients, respectively. The sensitivity was not found
to be significantly different from that of the Finn
Chamber test. The flare-up of eczema noted in 2
subjects also indicates that the test dose should not
be further increased. It can be concluded that a
patch test concentration of 600 mg/cm2of IMID
or DU in hydrophilic dried-in vehicle (TRUE-Test)
is adequate and safe.
It has been debated whether allergic reaction to
IMID or DU is based on contact allergy to the
compounds themselves or based on contact allergy
to formaldehyde. A positive response to IMID or
DU may then theoretically be due to a positive re-
action to the released formaldehyde. It can be cal-
culated that the maximum dose of formaldehyde
capable of being released in the IMID and DU
patches at the highest concentrations is 23 and 43
mg/cm2respectively, compared to 180 mg/cm2in the
formaldehyde patch in the TRUE Test standard
series. Studies of dilution series of formaldehyde
demonstrate that a few patients react positively to
formaldehyde concentrations as low as 23 to 43 mg/
cm2(14–16). In the present study, 5 out of 23 pa-
tients reacted at D7 to DU or IMID alone, while
18 out of 23 reacted to 1 of the biocides and to
formaldehyde, or to formaldehyde alone (Fig. 4).
In a study of 2400 consecutive patients, it was re-
ported that of the 13 patients positive to DU, 7
had no reaction to formaldehyde (7). In a study of
639 patients including 58 DU positive patients,
12% reacted to DU alone, 7% to DUπIMID, 7%
DUπformaldehyde (10). A recent study demon-
strated that 39% of the IMID-positive patients had
a concomitant formaldehyde reaction (17). Our re-
sults show that although some positive reactions
may be caused by release of formaldehyde, specific
positive allergic reactions to the biocides are also
likely to occur.
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Department of Dermatology
Gentofte University Hospital
Niels Andersens Vej