During April 1982, a poison ivy-like dermatitis affected 54 persons who consumed cashew nut pieces sold by a Little League organization in a southcentral Pennsylvania community. The cashew pieces, sold in 7-oz. bags, were imported from Mozambique and processed for distribution by a Pittsburgh company. The Little League had purchased 2,928 bags from a local distributor, and another 4,512 bags were sold by a distributor in small quantities throughout south-central Pennsylvania and northern Maryland.

Of 322 people interviewed who had purchased cashews from the Little League, 54 (20%) of 274 who ate cashews developed pruritic rash; none of the 48 who did not eat cashews developed rash (p 0.01).

Illness histories were obtained for 31 persons; 21 (68%) were male. Pruritic rash beginning 1-8 days (median 2) after cashew consumption and lasting 5-21 days (median 7) was reported by 29 persons; rash occurred on: extremities--97%, trunk--66%, groin--45%, axilla--34%, buttocks--21%. In addition, four persons reported perianal itching, and three reported blistering of the mouth. Thirteen (42%) of the 31 persons saw physicians; none required hospitalization. Patients' ages ranged from 9 to 72 years (median 32). Cashew-extract patch testing of 19 persons did not reliably predict clinical illness.

Fourteen bags of cashews were opened and visually inspected; five (36%) contained pieces of cashew shell. The absence of cashew shell from 2/3 of the bags may account for the lack of correlation between patch-testing results and clinical illness.

The Food and Drug Administration, the Pennsylvania Department of Agriculture, and the Allegheny County Health Department were informed of the investigation, and each inspected the processing plant independently and reported no obvious violations in processing cashews. Reported by R Aber, MD, J Marks, MD, Hershey Medical Center, T DeMelfi, MA McCarthy, E Witte, VMD, E Moore, CW Hays, MD, State Epidemiologist, Pennsylvania State Dept of Health; Special Studies Br, Center for Environmental Health, CDC.

Editorial Note

Editorial Note: The cashew tree, Anacardium occidentale, belongs to the same family of plants (Anacardiaceae) as the Rhus species, which cause poison ivy, poison oak, and poison sumac (1). This tree bears a pear-shaped fruit called the cashew apple. On the distal end of the fruit is the cashew nut, which is not encased in the pulp of the fruit. It is composed of an inner kernel and a double layered outer shell. Between the layers of shell is an oil containing 12 chemically distinct antigens, including cardol and anacardic acid, which are immunochemically related to the pentadecylcatechols found in the Rhus species (2). These oils have irritant and allergenic properties. Cashew nuts are partially processed before importation into the United States to remove shells and oil, and then cooked and packaged before distribution.

Pruritic dermatitis is a common problem among workers who shell the nuts by hand (3). Modern processing equipment has reduced the frequency of dermatitis among workers, and has increased the efficiency of oil extraction from cashew nuts.

This report documents what may be the largest outbreak of cashew nut-related dermatitis among persons not working directly with the raw nut or its oil. A previous report described six cases of dermatitis among dock workers who unloaded whole, unprocessed nuts, one case in a person who shelled and ate raw cashews, and one case in a chemist who prepared an ether extract of cashew nut oil (4). A second report described four cases of vesicular dermatitis among children who played with souvenir toy burros made of cashew nuts and beads wired together (5). A third report described five cases of generalized eczematous dermatitis among persons who ate raw cashew nuts; all five were also exquisitely sensitive to Rhus antigen (6).

Hypersensitivity to Rhus antigens appears to overlap hypersensitivity to cashew nut oil allergens, and hence, incompletely processed cashew nuts may pose a health risk to persons sensitive to poison ivy, poison oak, or poison sumac.

References

1. Cronin E. Contact dermatitis. New York: Churchill Livingstone 1980:475-87.

2. Mitchell JC, Rook A. Botanical dermatology: plants and plant products injurious to the skin. Vancouver: Greengrass Ltd 1979:66-7.

3. Bedi BM. Cashewnut dermatitis. Indian J Dermatol 1971;16:63-4.

4. Downing JG, Gurney SW. Dermatitis from cashew nut shell oil. J Indust Hyg Toxicol 1940;22:169-74.

5. Orris L. Cashew nut dermatitis. NY State J Med 1958;58:2799-800.

6. Ratner JH, Spencer SK, Grainge JM. Cashew nut dermatitis. An example of internal-external contact-type hypersensitivity. Arch Dermatol 1974;110:921-3.

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