Two entirely different mechanisms. In "lactose intolerance" (aka, 
lactase deficiency) , your body lacks the lactase enzyme necessary to 
process the milk sugar. The result for many typically includes gas, 
diarrhea, bloating, stomach cramps, etc. A dairy allergy is an 
allergic reaction, whereby your body identifies milk proteins as 
"foe" and goes on alert (and attack). The typical symptoms are as you 
describe - itching, hives, difficulty breathing, etc. It can (but 
does not always) include gastrointestinal symptoms such as vomiting.

We could go "non-medical" and say that both are the body not 
tolerating a particular type of food, but I think that just muddies 
the distinctions we make via accepted uses of terminology.

By the way, some of us truly don't "tolerate" dairy products, being 
both lactose intolerant and dairy allergic. :-)

Mark

At 02:36 AM 2/7/2007, you wrote:
>It's interesting that you mention the intolerance. I can't help but 
>suspect it's the same as allergies even though a lot of people think 
>they're two different things. I think it's because doctors insist 
>they are two different things, but an allergy is a negative reaction 
>to something right? Your body cannot "tolerate" what has been 
>ingested because it senses something not right or is not able to 
>handle what is there.