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EC number: 221-070-0
CAS number: 2997-92-4
Table 1: Results of patch tests at 3 days
All patients were engaged in the final production process of this
chemical, and none of the workers who were exposed to either the raw
materials or the intermediates formed during the chemical's synthesis
complained of dermatitis similar to that seen in our patients. All
patients showed strong positive reactions to AAPH on patch testing, and
their dermatitis improved after the production of AAPH was discontinued.
According to the manufacturer, the final product was highly purified and
the concentrations of contaminants, if any, were considered to be quite
low. Therfore, it is most likely that AAPH itself was the causative
agent of the contact dermatitis in these patients, although allergy to
other materials used in the production process or possible contaminants
in the final product s cannot be strictly ruled out. From our
investigations in this plant, contamination of protective rubber gloves,
during scraping-out of products from the tanks for purification, was
suspected as being causative of this occupational contact dermatitis.
The reactions to AAPH were negative in all control subjects, indicating
that this chemical probably acted as an allergen rather than as an
irritant. This was also supported by the clinical observation that most
patients suffered occasional eruptions for as long as 1-2 years after
production of AAPH had been discontinued. The recurrence of skin lesions
may be due, at least in part, to contact with AAPH remaining in very
small amounts in the workplace despite several rounds of cleaning.
Concerning the results of patch testing for materials other than
AAPH, many patients showed positive reactions to urushiol, nickel, and
cobalt. It is not surprising that 6 out of 8 patients were allergic to
urushiol, because there are numerous urushi plants in the woods and
forests in this part of Japan, and the rate of positive reaction to
urushiol in standard patch testing is reported to be about 80% for
patients with dermatitis in this region. There were no urushi plants in
the factory yard, however, and Japanese lacquer made from urushi had not
been used in this plant. The reason why so many patients showed a
positive response to metal allergens such as nickel is unclear. Some of
the positive or weakly positive reactions in case nos. 1 and 3 may be
due to the "excited skin syndrome", as both patients showed positive
responses to many allergens. Metal-containing chemicals were not used in
the synthesis of AAPH. However, as all patients had been engaged in the
production of various chemicals before the manufacturer started to
produce AAPH, they might have been sensitized to these allergens through
their previous work.
2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) is an azo
compound which has been used as a radical chain initiator. The purpose
of this study was to confirm contact sensitivity to AAPH in individuals,
who were engaged in the production of AAPH, and presented with prolonged
eczematous eruptions, mainly on exposed areas. Patch testing was carried
out with AAPH (1 and 5 % aq.) on 8 patients and 6 healthy volunteers who
had never been exposed to this chemical. All patients showec a strong
positive patch test reaction to this agent, while all control subjects
showed negative results. Because this chemical has recently been used
for studies on the oxidation of biological material, not only production
workers in the chemical industry but also medical researchers should
avoid prolonged exposure to this agent.
2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) is a
water-soluble radical chain initiator, which has been used not only in
the chemical industry but also in the field of experimental medicine and
biochemistry. In 1994, workers who were engaged in the production of
AAPH in a chemical plant complained of itchy eczematous eruptions,
mainly on exposed areas such as the hands and forearms. As a result of
patch tests in these patients and control subjects, AAPH was confirmed
to be the causative agent of this outbreak of contact dermatitis. As far
as we are aware, this is the 1streport of contact allergy to
AAPH, except for an unpublished document.
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