In this thread about cooking for people with allergies the first commenter (rightly, IMHO) suggests splitting up that general effort into more allergy-specific tips. The overall effort might still be worthwile, but as I suffer from the 'fruit/nut' allergy myself, I would like to start this question & answer.  My question: which foods trigger the fruit/nut allergy, rated by severity, and what techniques can you use to reduce the effect? I will be answering my own question as well (in the hope of offering some help), but would prefer answers that I don't know already.  For those that aren't aware of the allergy for nuts and fruits and wondering whether they may have it, here are links to wikipedia on oral allergy syndrome and the Calgary Allergy network (as I find their site useful and will be using it, and my own experience, as a departure point. Note that the allergy may start later in life. 
A few basics which haven't been mentioned:   Find out what people's allergies are before they come (they should tell you, but better to ask) Make labels which list food ingredients and put them on your buffet. Bring an epi-pen.  