The so-called raw cashews sold in natural food stores are not exactly raw, but instead are steamed. It is the case that the double shell surrounding the raw cashew, which is technically a seed and not a nut, contains urushiol, a resin that can create significant skin rashes, and can be toxic when ingested.
Urushiol is the same chemical found in poison ivy, and it is present on the leaves of the cashew tree as well as in the raw cashew shell. Processing raw cashews can be a laborious and nightmarish ordeal, and people who work in cashew processing plants tend to exhibit greater allergies to cashew shells over time. There is a high incidence of skin rashes among people who either harvest or process raw cashews. Greater sensitivity to urushiol can lead to extreme allergic reaction when raw cashews are ingested, and anyone allergic to poison ivy could potentially have a fatal reaction to eating true raw cashews.