Food allergies

Development of food allergies 

If you've been paying attention at all the past decade or so, you will have noticed an increase in food allergies. From peanuts to milk, it seems everything edible is able to kill someone somewhere. Or at least make them very unhappy. Allergies to anything is an immune response to a foreign thing your body wants to get rid of. In the case of food allergies, some chemical or ingredient in what you eat can cause anything from mild stomach upset to severe anaphalactic shock and airway closure. 

It is estimated by the NIH that 20% of children under the age of 5 suffer from food allergies, and 25% of adults have one or more. Sometimes you can 'grow out of' allergies, but you can also develop new allergies as an adult. There are also allergies which are exercise-induced, or cross-reacting allergies. Mayo Clinic's website has this handy table:

If you are allergic to:	Birch pollen	Ragweed pollen	Grasses	Mugwort pollen
You may also have a reaction to:	Apples Carrots Celery Hazelnuts Peaches Pears Raw potatoes	Bananas Melons (cantaloupe, honeydew and watermelon) Tomatoes	Tomatoes	Apples Carrots Celery Kiwi fruit Peanuts Some spices (parsley, coriander, or caraway, anise, and fennel seeds)

Food allergies are also on the rise, making the public more aware. We probably all know at least one friend or family member who is lactose-intolerant, can't eat eggs, or will swell up like a balloon if you give them Pad Thai. (Because of the peanut sauce.)

This comic is from the talented Tyler at Forbidden Ferret, a daily educational webcomic.

How do you become allergic?

Allergy development is a two-step process. The first time you are exposed to an allergen, your immune system recognizes the invader and produces antibodies which specifically bind to that one molecule. These antibodies then circulate in your blood and body for a long time. If you are exposed to the same antigen (food) again, those antibodies recognize it, bind to it, and signal your body to attack by releasing things like histamines. Those cause swelling, inflammation, redness, itchiness, etc. 

Image from a document titled Specific Resistance Immunity.

Ironically, allergies tend to happen with a food that is eaten often. For example, Japan has a higher incidence of rice allergy than the US. If someone you are with eats a food and begins to have trouble breathing, breaks out in hives or a rash, faints, or begins vomiting, you should seek medical help immediately. For a full background of allergies, causes, symptoms, and how you should react to an allergy in someone, see the NIH booklet. 

In infants and children, the most common food allergies are:

• Eggs
• Milk
• Soy
• Peanuts or tree nuts
• Wheat

While in adults, the most common food allergies are:

• Shellfish (shrimp, crab, oyster, lobster, crayfish)
• Peanuts and tree nuts
• Fish, such as salmon

Children tend to outgrow egg, milk and wheat allergies. Peanut allergies tend to be for life, and allergies developed as an adult tend to stick around as well. Food allergies are also not the same as a food intolerance. As I mentioned lactose intolerance earlier, it is important to note that the immune system is not involved, there are no antibodies made to milk. You body simply cannot digest the lactose in milk, thus meaning you are intolerant, not allergic. Other common intolerances are MSG, gluten, and sulfates.

 

What can I do?

For pregnant women, it is recommended that you breast-feed newborns for at least the first four months. There are many, many health benefits to this practice, plus it is far more economical than formula. Not to mention the bonding time. There is no conclusive evidence yet that the mother avoiding common allergenic foods will prevent the child from developing allergies. So go ahead and have your cereal with milk, toast with peanut butter, and an omelet. 

One way to identify what you are allergic to is to keep a food diary of how you feel after eating different types of foods. This could identify triggers. Then you can try an elimination diet, where any foods which caused an allergic reaction are eliminated one by one so you can see if that causes your reactions to stop. You should always consult your healthcare provider before altering your diet significantly. To test reactions to specific foods, you can request a skin prick test. Your health care provider will prick your skin with a needle and place a small amount of food extract under your skin. If you have swelling and redness, this is a positive reaction, meaning your immune system responded. A blood test is a bit more extreme, where the actual levels of IgE antibodies to a specific food are measured in your bloodstream. 

The easiest way to avoid allergic reactions if you already know you're allergic is to keep your living area clean. If you are allergic to peanuts, even the dust, keep peanuts out of your kitchen, wash surfaces and vacuum regularly. You can also obtain a medical warning bracelet from your doctor, as well as an epinephrine pen. Commonly called "Eip Pens", using these is the best immediate way to counter-act anaphylaxis. It will flood your system with epinephrine, which calm down the histamines and hopefully allow you to continue breathing. 

Where can I learn more?

The next Food Allergy Awareness Week is May 11-17, 2014. The Food Allergy Research and Education (FARE) group has all kinds of fun activities and information. They also have lots of great resources about how to deal with allergies in children, in public places like camp and restaurants, allergy statistics, how to read food labels, and more.

MedLinePlus has a link to the NIH overview PDF, as well as links to various clinical trials that have been done for different allergies, management help, and specific resources for each type of food allergy.

Of course we always have WebMD for various symptoms, treatment, and related diseases. 

Please feel free to share any allergy-related stories or advice you have!