Anaphylaxis vs. 'bad allergy reaction'?

Dear LungLine Nurse,
How do you tell a bad allergy reaction from anaphylaxis?  I've had numerous "bad" allergic reactions, ranging from hives where my neck turned scarlet and was covered with hives (from accidentally eating shellfish or having something around my neck that I was allergic to) to having difficulty breathing and wheezing (asthma induced by inhaling and/or unknowingly ingesting sulfites and/or large amounts of MSG).  
Is the difference between a bad allergic reaction and anaphylaxis a matter of whether the reaction starts getting worse & becoming more systemic?  Since you're supposed to start treating for anaphylaxis right away, HOW LONG is it safe to wait to see if you respond to other measures (albuterol MDI or antihistimine) before deciding whether to seek additional aid and/or use an epi-pen?  So far, none of my prior doctors suggested my having an Epi-pen and my reactions all subsided over time.  My current allergist and I have been discussing whether I should have an Epi-pen prescribed.
I am 44 and have had asthma and allergies to shellfish, sulphites and MSG all my life.
I have read the excellent National Jewish MedLine article on anaphylaxis, but have never really had this point clarified.  Thank you.
Starion

[National Jewish]

Anaphylaxis is usually reserved for an allergic reaction that occurs relatively quickly and involves more than the skin. Having swelling in your throat and airways (difficulty breathing and wheezing) falls into the category of anaphylaxis.
As far as having and using an Epi-Pen, there is no risk at all by having one!! Having the symptoms you described makes the case for having an Epi-Pen with you. As far as using it, some physicians will say that anyone experiencing anaphylaxis where the airways are involved is enough justification for using adrenaline when the allergic reaction occurs. This has been shown to save the lives of many people. Waiting for significant difficulty to occur takes on a greater risk. I would suggest discussing this with your allergist.

[starion]

Dear LungLine Nurse,
I had a long discussion today with a dermatologist.  She said that because I can eat small quantities of foods I'm sensitive to without discernable reaction I am merely SENSITIVE not ALLERGIC.  She also said that I could continue to eat carefully controlled portions of these foods.
She also said that because my reactions to shellfish were just hives & didn't involve shortness of breath or tightening of my throat or other signs of systemic involvement, hives are just skin reactions, no matter how red, inflamed, itchy, or widespread or long duration--hours, days, weeks; these reactions are just uncomfortable & not life-threatening.
We are both puzzled about whether I might react internally (e.g. via respiratory system) to food allergens and now show any skin reaction, like I did with the food additives.  Any clarifications or resources or references you could suggest would be greatly appreciated.
Aloha,
Starion

[starion]

Dear LungLine Nurse,
Thanks for your advice.  I will continue my discussions with my allergist and pulmonologist.  I will also get and learn to use an Epi-Pen.
Aloha,
Starion--grateful in HI