Cashew nuts are not new to the American diet, but cashew apple is.
Cashew trees native to Brazil and the West Indies also grow in Central America, Asia and Africa. People in these countries have long eaten not only the cashew nut, but the apple itself.
The cashew apple has a fibrous juicy pulp which can be eaten directly or squeezed to make cashew apple juice – a rich source of vitamin C and antioxidants.
This juice is starting to appear in American health food stores. Despite its healthy nature, it can be a source of allergic difficulties.
As it turns out, the cashew tree is a member of the Anacardiaceae Family, which includes poison ivy and oak, poison sumac, mango, lacquer tree, Indian marking tree and rengas tree.
The common allergen found in all these plants is urushiol and hence, there can be cross- reactivity with all the plants.
In the case of the cashew, the apple has a higher concentration of urushiol than the nut. Hence, it has greater likelihood to lead to allergic problems. These can occur via contact with the skin, resulting in the typical poison ivy-type rash of itchy bumps and blisters. Ingestion can cause irritation of the lips, tongue, mouth and GI tract.
Of special interest is that ingestion of cashew nut or cashew apple can lead to reappearance a previously healed case of poison ivy/oak. It seems the area of the skin that broke out from contact with urushiol has immunologic memory that can cause the same area to redevelop the rash from ingestion of urushiol.