(NBC NEWS) -- From fad diets to famous dogs, Americans spend billions of dollars avoiding certain foods or favoring certain pets because of allergies.
But experts say they may be feeding an allergy fear that science can't back up.
Americans spend about 7-billion dollars on gluten-free foods every year.
Many think they have a gluten allergy.
The thing is, true gluten allergies are extremely rare.
"Just the fact that I say it's not an allergy doesn't mean that you're not having um perhaps an adverse reaction to the food," said one doctor.
It's more likely people may simply be sensitive to gluten, found in products with wheat, barley or rye.
"Now that I stopped eating, I mean, that I started eating new diet, gluten-free, I feel a little bit better," one person said.
Experts say most allergy myths begin with the experts themselves and their theories that don't pan out.
One other myth about allergies, there's no such thing as a truly hypoallergenic dog like the Portuguese Water Dog President Obama promised his girls.
It's true some breeds are easier on people with allergies, like Malia Obama.
But it's generally not the fur that makes people sneeze it's the allergens that are released in saliva and other glands.
Experts 'advice people with pet allergies to get a fish.
Experts say evidence is now mounting that parents don't need to delay giving their young children peanuts and eggs. It now appears early introduction of allergenic foods might promote tolerance.