| I would like to clear some misconceptions on this thread. I am the author of "The poison Oak & Poison Ivy Survival Guide."
Poison Oak, Poison Ivy, Poison Sumac, Mango, Cashew are members of the family Anacardiaceae.The family splits off into genus and Poison oak/ivy/sumac are in the genus Toxicodendron (certain botanical features to be in this genus), and Mango and Cashew are in others. The allergenic oil urushiol is only in the Toxicodendrons.
Mango's allergenic oil is a resorcinol. The cashew has two allergenic oils in the honey-combed shell, anacardiol and cardol. The oil in the cashew nut is harmless. American cashews have been heated to deactivate any allergenic that migrated from the shell to the nut—even the ones labeled raw. Although "mistakes" have happened.
Even though they have different allergenic oil chemistries, all have similarities. If you are allergenic to poison oak/ivy, you are probably allergic to the others, and visa-versa. Cashew is not much of a problem, but the oil in the skin of the mango is. It is not as strong as that of poison oak/ivy though. The pulp does not contain the oil naturally, but it migrates into the pulp a little ways from the skin according to studies.
I would definitely suspect mango in the mix, but for such an extreme reaction, you would have probably already have had an acute sensitivity to poison oak/ivy. Also, the reactions you had are not normal. Stomach upset, and fever are, but the ear thing sounds more like a mold allergy. Some dried fruit contain mold and also sulfur (an allergen also). The rash definitely has poison oak/ivy/mango characteristics if it did not arise with an hour of eating the food, because this type of allergy is a delayed contact dermatitis, whereas if it happened within an hour, it would be immediate contact dermatitis-hives.