First of all, we were talking about drug and vaccine allergies.
OK, with you so far. Most of these aren't of course allergies against the vaccine as such, but to all the other components. (Flu vaccine being produced using chicken eggs being the most well known problem. They're often quite good at removing any traces of egg protein, but the process is by no means perfect, and for many sufferers getting the shot in a setting with emergency medical services to hand, as in "sitting on the chair right next to you" is often indicated. It's not for nothing that roughly 3/4 of all cases of anaphylaxis is iatrogenous.
Secondly, I specifically mentioned the different types of allergies possible INCLUDING the textbook example, celiac disease. Celiac disease absolutely IS an allergy, being a Type IV (delayed-type) hypersensitivity reaction which gives a specific set of GI symptoms in people who know they have the disorder.
No. Celiac disease is not an allergy per se. It is a specific autoimmune disease. One major difference between the two is that in autoimmune diseases the body's immune system attacks the body's own tissues, which is not a part of an allergy response. Allergies will not destroy your own tissues (though prolonged inflammation is of course no sinecure). Auto immune disease, (such as Celiac disease) will in many cases destroy tissue. In severe cases surgical intervention/removal of the tissue is indicated, and indeed loosing your intestine to the surgeons knife is a known complication of untreated Celiac disease. That's never the case with allergic reactions. (That's one difference, there are others).
The familial tendency towards allergy manifsts itself as asthma/atopy/allergic rhinitis, not with allergies to specific drugs or foods.
Never said it did. Read was I wrote again. What I did say is that allergic reactions in certain tissue has a hereditary component, i.e. respiratory vs. gastro intestinal. This connection is weaker though. In this case, the family had a supposed history of gastro intestinal involvement, so that's a point in favour of that hypothesis then.
Also you should know that the blood test (RAST) is absolutely worthless to determine if somebody is allergic to something if they have never been exposed to it before, such as for drugs.
Yes, and in this case the patient complained of symptoms after having taken the drug, which is an exposure. So what's your point? The main problem with these test are actually the opposite one. Just because you have been exposed and developed anti bodies that doesn't necessarily mean you'll have enough symptoms to qualify as "allergic" to that substance, especially when your counts of antibodies are low. Though, avoidance is currently thought to be indicated though there is currently a small but growing number of researchers that question this course of action. Time will tell.
Basic immunology such as that should have been covered in your general college biology classes
Ah! "There's your problem". We've moved quite a bit from what would be covered in basic biology. If that's what you're basing your understanding of allergies and allergic reactions on, you need to read up.