People use these words interchangeably, but they aren't the same thing.
Which one you're dealing with changes how careful you have to be, and
whether a crumb matters at all. This planner is built for the strictest
case, celiac disease. If you're casual about celiac, you do real damage.
Autoimmune
Celiac disease
Celiac disease isn't an allergy and it isn't an intolerance. When you eat
gluten, your immune system attacks the lining of your own small
intestine. Over time, that damage causes the long term problems.
The damage happens whether or not you feel anything that day. "A little
bit won't hurt" is wrong for exactly that reason. It's also the
hardest thing to explain to people who mean well.
How strict
Total, for life. Even trace amounts count. A shared toaster or a shared fryer is enough to cause a reaction.
How common
Roughly one in a hundred people.
Allergy
Wheat allergy
This one is a true allergy. The immune system reacts to wheat proteins,
not to gluten specifically. A reaction can come on fast and it can be
severe, up to and including anaphylaxis.
With a wheat allergy, "gluten free" is the wrong filter, and it's wrong
in both directions. Barley and rye contain gluten but they aren't
wheat. And "gluten free" on the front of a pack tells you nothing
about the other allergens inside.
How strict
Strict about wheat, but what counts is different from celiac. You're reading labels for something else.
Over time
Many kids outgrow it. Celiac disease doesn't work that way.
Sensitivity
Non-celiac gluten sensitivity
People get real symptoms after eating gluten, but without the autoimmune
damage of celiac disease and without the allergic reaction of a wheat
allergy.
Doctors diagnose it by ruling the other two out first. Researchers still
haven't settled on what causes it. For some people, other parts of
wheat seem to be the trigger, not the gluten.
How strict
Usually guided by symptoms, not by damage, so trace exposure tends to matter less. Ask your doctor how strict you need to be.
Testing
No single test confirms it. Celiac disease has to be ruled out properly first.
Choice
Gluten free by preference
There's no medical reason behind this one. If you don't have one of the
conditions above, cutting gluten hasn't been shown to do anything for
you. Gluten free processed food also tends to carry less fiber and
more sugar and fat than the food it replaces.
You still need to know about it. Some kitchens hear "gluten free" and
think it's a preference they can accommodate, not a medical
requirement. A lot of cross contamination starts right there.
How strict
Whatever you like. This is the group the strict ones get mistaken for.
Get tested before you cut gluten out
Celiac tests look for your body's reaction to gluten. If you've already
stopped eating it, the tests can come back negative even when you do
have celiac disease. You may then be asked to eat gluten again for
weeks before anyone can retest you, and that's a miserable thing to
hear after the fact. If you think it might be celiac, talk to a doctor
before you change what you eat.
This is background information. It isn't a diagnosis and it isn't medical
advice. Testing, diagnosis, and how strict your own diet needs to be are
all things to work out with your doctor or a dietitian.