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00:00Don't worry.
00:06These aren't peanuts, they're pretzels.
00:09Dear Tim and Moby, why isn't my sister allowed to eat peanuts?
00:14From Amanda.
00:15Well, your sister probably has a peanut allergy.
00:20An allergy is a sickness of the immune system.
00:23Normally, the immune system protects your body against germs.
00:27It starts treating harmless stuff like peanuts as if they were dangerous.
00:32This reaction sometimes causes annoying symptoms like a runny nose, sneezing, or a rash.
00:38It can also cause an asthma attack, a narrowing of the airways in the lungs that makes it
00:42hard to breathe.
00:45Or in some cases, it can get much worse with a swelling reaction all over the body called
00:49anaphylaxis.
00:51Swelling in the windpipe can make it impossible to breathe at all if it's not treated immediately.
00:57But allergies cause the immune system to go kind of haywire.
01:02That's why some allergies can be really dangerous.
01:05We all need to do whatever we can to help people with severe allergies avoid the things
01:09they're allergic to.
01:11Well, there are lots of different allergens, things that can set off an allergic reaction.
01:18And they can enter the body in all kinds of ways, through eating and drinking, breathing,
01:22or just from skin contact.
01:24Besides peanuts, some of the most common food allergies are eggs, milk, wheat, tree
01:29nuts, soybeans, shellfish, and other kinds of fish.
01:34Pollen from flowers and trees gives millions of people itchy eyes and runny noses every
01:39spring.
01:40Bee and wasp stings can be really dangerous if you're allergic to them.
01:45And just about everyone knows someone with an allergy to cats or dogs.
01:49But remember, these allergens are only dangerous if you're allergic to them.
01:54Well, a healthy immune system recognizes which substances are actual threats to the body,
02:00like bacteria and viruses.
02:03To fight off these invaders, the immune system forms molecules called antibodies.
02:08These identify and destroy germs.
02:11When an invader is detected, that typically triggers the release of a substance called
02:14histamine.
02:16It speeds the immune response by causing infected tissue to swell with antibody-rich fluids,
02:23which can have some unpleasant side effects, like a runny nose.
02:26But it's necessary to get rid of dangerous invaders.
02:30Unfortunately, in people with allergies, histamine is released in response to harmless things
02:35like roses, or even helpful things like the antibiotic penicillin.
02:41Anaphylaxis is a histamine response in overdrive.
02:45That's why tissues all over the body swell dangerously.
02:48Well, doctors can see if you have allergies by performing a scratch test.
02:54Bits of common allergens are scratched onto the skin to see whether your body overreacts
02:58to any of them.
03:00In kids, blood tests are more common because a scratch test might trigger an allergy.
03:05Once someone knows what they're allergic to, they can make an effort to avoid those allergens.
03:10Medicines with antihistamines can make them more comfortable if they're exposed.
03:15But those aren't enough to treat anaphylaxis.
03:18People with severe allergies often carry an EpiPen for emergencies.
03:22It's an injectable medicine that treats symptoms immediately.
03:25Now, can I please have my pretzels?