Fatal asthma in a child
after use of an animal shampoo containing pyrethrin
Sheldon L Wagner, Department of Environmental and Molecular Toxicology Oregon
State University Corvallis, OR 97331-7301, wagners@ucs.orst.edu
To the Editor,
An 11-year-old girl had been diagnosed with asthma at age
6 years. She had never been hospitalized and had rarely received steroids. Her
only medication was albuterol, which was taken by inhaler as needed. On the
day of admission, she gave her pet dog a bath using a shampoo containing 0.2%
pyrethrin. She had used this shampoo 2 years earlier, with a brief but mild
increase in her asthmatic symptoms that lasted 48 hours. The dog had been in
the family home for several years. She was asymptomatic when she started to
bathe the animal. Within 10 minutes, severe shortness of breath with wheezing
developed, and she was immediately transferred to a hospital. She was
intubated and treated aggressively for an acute asthmatic attack. She did not
respond to treatment and died about 2-1/2 hours after the initial exposure to
the pet shampoo.
At autopsy, there was mucous plugging of the bronchioles
with an inflammatory infiltrate composed of neutrophils and eosinophils. There
was prominent vascular congestion, and many alveolar spaces contained
homogeneous eosinophilic edema fluid. The cause of death was listed as
"respiratory arrest secondary to acute asthmatic attack." The
pathology findings were consistent with the literature on pathologic changes
in acute asthma.1
The pyrethrin class of insecticides was originally
formulated from plants of the Compositae family, which includes daisies and
chrysanthemums. Pyrethrum refers to both the crude plant extract and the
marketed formulation of insecticide. Pyrethrin is the insecticidal chemical
prepared from pyrethrum flowers, and it is also a market name for purified
pyrethrum. A third term, pyrethroid, refers to insecticides of the same class,
but these are synthetic compounds. Pyrethrum is known to cause allergy,
including asthma and allergic skin disease. A review in 1934 warned physicians
about its allergenic properties.2 Our case is the first documented case of
allergy to pyrethrin. No cases of pyrethroid allergy have been documented.
Neither pyrethrin nor pyrethroids are currently
classified as allergens by the Environmental Protection Agency. Techniques of
extraction from the flower have greatly improved the purity of the original
pyrethrum formulations, and a recovery of 95% to 97% pyrethrin is now
achievable.3 The insecticide is, therefore, commonly marketed under the name
of Pyrethrin, but it may contain small, but still allergenic, amounts of the
impurities found in the crude extract. One suspected allergenic impurity is
oleoresin, which may have been responsible for the allergic reaction in our
case. The mechanism of allergy from pyrethrins is poorly documented. The
marketing of pyrethrin is favored over that of pyrethrum, based on skin test
studies suggesting that it is safer.4 Although physicians have access to crude
pyrethrum for skin testing, its purified isomers or mixtures of isomers are
available only in the research laboratory. They are too expensive for
practical use.
The possibility of an acute allergic reaction occurring
from the use of any currently marketed pyrethrum insecticide should be
considered in any case of respiratory or dermal allergy of unknown cause. This
case suggests that physicians should also be alert to formulations marketed as
pyrethrin. Pesticides of this class are being used with increasing frequency
in homes and are easily available to the public. Manufacturers are not
required by the Environmental Protection Agency to state on the label that the
pyrethrum formulations are allergens.
References
1.Roche WR. Inflammatory and structural changes in the
small airways in bronchial asthma. Am J Respir Crit Care Med1998;
157(suppl):S191 -S194.[Medline]
2.Feinberg SM. Pyrethrum sensitization. JAMA1934;
102:1557 -1558.
3.Carlson DJ. Pyrethrum extraction, refining, and
analysis. In: Casida JE, Quistad GB, eds. Pyrethrum. Flowers. Production,
Chemistry, Toxicology, and Uses. New York: Oxford University Press; 1995:
97-107.
4.Zucker A. Investigation of purified pyrethrum extracts.
Ann Allergy1965; 23:335 -339.
Original: http://www.ewjm.com/cgi/content/full/173/2/86?ijkey=DPnndLnkuLjHU
