# How do allergies work? **URL:** \ **Category:** Factual Questions\ **Created:** [March 23, 2004, 8:22pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977 "2004-03-23T20:22:23Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![MsWhatsit](https://avatars.discourse-cdn.com/v4/letter/m/eb8c5e/32.png) [@MsWhatsit](https://boards.straightdope.com/u/MsWhatsit)\ **Post date:** [March 23, 2004, 8:22pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/1 "2004-03-23T20:22:23Z")
I know a lot of people are diagnosed with allergies these days. But how does a person develop an allergy? Is it something you’re born with or something you develop? If the latter, how does that happen? And once you have an allergy, how come some people get exposed to an allergen but only sneeze a lot or break out in hives, but other people go into shock and have to be transported to the ER? Also, what are the most common allergens? ---
**Author:** ![Mr.Kobayashi](https://avatars.discourse-cdn.com/v4/letter/m/4af34b/32.png) [@Mr.Kobayashi](https://boards.straightdope.com/u/Mr.Kobayashi)\ **Post date:** [March 23, 2004, 8:45pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/2 "2004-03-23T20:45:16Z")
> [@MsWhatsit](#): > > I know a lot of people are diagnosed with allergies these days. But how does a person develop an allergy? Is it something you’re born with or something you develop? If the latter, how does that happen? And once you have an allergy, how come some people get exposed to an allergen but only sneeze a lot or break out in hives, but other people go into shock and have to be transported to the ER? > > Also, what are the most common allergens? According to WebMD: Allergies are an overreaction of the immune system. The immune system normally protects the body from viruses and bacteria by producing antibodies to fight them. In an allergic reaction, the immune system starts fighting essentially harmless substances like dust mites, pollen, or a medication as though these substances were trying to attack the body. This overreaction causes problems that affect the skin, nose, lungs, digestive organs, and blood vessels. Allergic reactions may not occur the first time you are exposed to an allergy-producing substance (allergen). For example, the first time you are stung by a bee, your body’s response may be only pain and redness from the sting. With subsequent bee stings, allergic symptoms, such as hives or difficulty breathing, may occur. This is caused by the response of the immune system. ---
**Author:** ![Doomtrain](https://avatars.discourse-cdn.com/v4/letter/d/0ea827/32.png) [@Doomtrain](https://boards.straightdope.com/u/Doomtrain)\ **Post date:** [March 23, 2004, 9:18pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/3 "2004-03-23T21:18:27Z")
> [@MsWhatsit](#): > > Is it something you’re born with or something you develop? If the latter, how does that happen? It can be both from what I understand. The first time I was given penicillin, I had an allergic reaction, so it was presumably from birth. However, I ate nuts for years and was fine, until a couple years ago when I broke out in a nasty rash and have been the same since. ---
**Author:** ![Jayrot](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@Jayrot](https://boards.straightdope.com/u/Jayrot)\ **Post date:** [March 24, 2004, 12:55am UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/4 "2004-03-24T00:55:25Z")
Don’t forget – [How allergies work](http://health.howstuffworks.com/allergy.htm) ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [March 24, 2004, 2:21am UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/5 "2004-03-24T02:21:54Z")
This OP has been answered, but to get my money’s worth, I’ll give a brief summary. Altho most people are born allergic to some substances, some acquire an allergy later in life. The symptoms are primarily due to histamine; hence, you use antihistamines to control the reaction. However, in severe cases you will need epinephrine to control the Ig reaction. A mild reaction, which does not involve the immune process to such an extent, is called a sensitivity, not an allergy. For example, I’ve heard that people can be “sensitive” to poison ivy, not allergic. I guess it’s a matter of degree, but I’m not entirely happy with that dichotomy. ---
**Author:** ![akrako1](https://avatars.discourse-cdn.com/v4/letter/a/c77e96/32.png) [@akrako1](https://boards.straightdope.com/u/akrako1)\ **Post date:** [March 24, 2004, 9:04pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/6 "2004-03-24T21:04:17Z")
Something to thing about… Food allergies occur when food matter comes into contact with blood. Usually this is in the colon. Theoretically, this should not happen. By the time some people start to get older, they develop tiny tears in the colon, which brings food into contact with blood. The cause of these tears are debatable, but some think they are due to eating crappy food over the course of one’s life, or by eating a food one is intolerant to. This is why food allergies tend to show up later in life. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [March 24, 2004, 11:00pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/7 "2004-03-24T23:00:32Z")
> [@akrako1](#): > > Something to thing about… > > Food allergies occur when food matter comes into contact with blood. Usually this is in the colon. Theoretically, this should not happen. By the time some people start to get older, they develop tiny tears in the colon, which brings food into contact with blood. The cause of these tears are debatable, but some think they are due to eating crappy food over the course of one’s life, or by eating a food one is intolerant to. This is why food allergies tend to show up later in life. I don’t think that’s true. Many allergic reactions are caused merely by contact and many food allergies, such as to peanuts and strawberries, occur in childhood. [http://www.foodallergy.org/research.html](http://www.foodallergy.org/research.html) ---
**Author:** ![Doomtrain](https://avatars.discourse-cdn.com/v4/letter/d/0ea827/32.png) [@Doomtrain](https://boards.straightdope.com/u/Doomtrain)\ **Post date:** [March 24, 2004, 11:06pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/8 "2004-03-24T23:06:56Z")
Anyone have a decent cite for **akrako1** ’s claims? Sounds like BS to me. ---
**Author:** ![RayMan](https://avatars.discourse-cdn.com/v4/letter/r/e495f1/32.png) [@RayMan](https://boards.straightdope.com/u/RayMan)\ **Post date:** [March 24, 2004, 11:23pm UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/9 "2004-03-24T23:23:28Z")
Food does not necessarily need to be consumed for an individual with an extreme allergy to exhibit an allergic reaction. Some people with a peanut allergy, for example, need only _touch_ a surface which once had peanuts on it to go into anaphylaxis. I work with children, and food allergies are a huge concern these days. I am constantly faced with the challenge of trying to separate children with food allergies from children eating allergen-containing foods. Some of these children are so sensitive that they must sit at special, allergen-free tables. I frequently carry special epinephrin injection devices to inject children who have gone into anaphylactic shock. Thank goodness, I have not yet had to use one. ---
**Author:** ![GilaB](https://avatars.discourse-cdn.com/v4/letter/g/8e7dd6/32.png) [@GilaB](https://boards.straightdope.com/u/GilaB)\ **Post date:** [March 25, 2004, 5:42am UTC](https://boards.straightdope.com/t/how-do-allergies-work/235977/10 "2004-03-25T05:42:52Z")
> [@akrako1](#): > > Something to thing about… > > Food allergies occur when food matter comes into contact with blood. Usually this is in the colon. Theoretically, this should not happen. By the time some people start to get older, they develop tiny tears in the colon, which brings food into contact with blood. The cause of these tears are debatable, but some think they are due to eating crappy food over the course of one’s life, or by eating a food one is intolerant to. This is why food allergies tend to show up later in life. IANAD, but ‘tiny tears in the colon’ would lead to massive infection and shock as the huge numbers of many kinds of bacteria that live in your colon leaked into the abdominal cavity, which should normally stay sterile. Allergies would be the least of your worries. Allergenic molecules in food are small enough to cross into the bloodstream the same way that nutrients do, which definitely doesn’t involve shredded intestines.