Acid anhydrides are low-molecular-weight chemicals known to cause respiratory irritancy and
allergy. Skin
allergy has on rare occasions been reported. 2 workers contracted
hives and
itching on uncovered skin after 2 months exposure to
methyltetrahydrophthalic anhydride (
MTHPA) and methylhexahydrophthalic
anhydride (MHHPA), to which they had airborne exposure. Later, the patients also developed
conjunctivitis,
rhinitis,
sore throat,
cough or
asthma. In addition to
MTHPA, 1 worker was also exposed to unsaturated
polyester resin (UP). Both patients' immediate
allergy to
MTHPA and MHHPA was verified by positive prick tests to
MTHPA and MHHPA, conjugated with
human serum albumin (HSA), and positive radioallergosorbent tests (RASTs) to these
anhydrides. On prick testing, both patients also reacted to a
phthalic anhydride (PA)-HSA-conjugate and 1 of the patients to UP-HSA-conjugate. Specific immediate
allergy to UP was shown by RAST. RAST inhibition with
MTHPA, MHHPA and UP-resin conjugates confirmed
IgE-mediated
allergy and cross-reactivity between
anhydrides. Our patients had developed airborne contact
urticaria caused by
phthalic anhydrides, in addition to respiratory
allergy.
Phthalic anhydride contained in the UP resin was possibly responsible for the immediate reaction of the skin.