Dear Andrew, The "sumac family" you mentioned is indeed the one the Mango is in, although it's more properly known as the Cashew family (Anacardiaceae). The bark, leaves and peel of the mango contain a white, sticky sap that can cause an itchy rash. Also, the small, reddish-white flowers exude a volatile substance that is irritating to the respiratory tract. People who are known to have bad allergic reactions should stay away from it. Best Regards, James