We report the case of a 55-year-old male who experienced cough, dyspne
a, wheezing, and nasal congestion immediately upon exposure to FD&C Bl
ue Dye No.2 (Indigotine) at work. The patient had worked for 10 years
mixing and grinding powdered synthetic red, yellow, and blue dyes for
use in foods; symptoms had occurred for 2 years and only with exposure
to Indigotine (C16H8N2Na2O8S2), a free flowing blue powder. Prick tes
ting to Indigotine (20 mg/mL) was negative. ELISA failed to detect spe
cific IgE, IgA, IgM, or IgG to Indigotine-HSA conjugates. Bronchial ch
allenge was done according to the method of Pepys et al. beginning wit
h 4 x 10(-4) lactose dilution of Indigotine powder. After 5 minutes of
exposure to 4 gm Indigotine/100 gm lactose, the patients developed dy
spnea and audible wheezing. At 20 minutes postexposure, there was a 20
% decline in FEV(1) from prechallenge baseline; no late phase response
was observed. A second bronchial challenge with sodium sulfate, the m
ajor nondye product additive was negative. To our knowledge, this is t
he first documented case of occupational asthma due to FD&C Blue Dye N
o. 2. The pathogenesis is uncertain but does not appear to be IgR medi
ated.