Food allergy 101: causes, symptoms, & treatment

Food allergy 101: causes, symptoms, & treatment

Many people seem to have food allergies, but many of us don’t seem to understand them. Why not understand the basics – food allergy 101?

Food Allergy 101

food allergy 101-food allergies-food bourn allergies-peanut-soy-milk allergy-egg allergies-tree nuts allergy-wheat allergies-shellfish allergies-fish allergy

Food allergy is an abnormal response to certain food triggered by your body’s immune system. The immune response (“an allergic reaction”) occurs when your immune system wrongly recognizes some of the proteins in food as harmful and launches protective measures such as releasing chemicals like histamine, which causes inflammation. The proteins that trigger the reaction are called allergens.

2 Types of food allergies

  • IgE antibody
  • non-IgE antibody

Antibodies are a type of blood protein used by your immune system to recognize and fight infection.

  • In an IgE food allergy, the IgE antibody is released by your immune system.
  • In a non-IgE food allergy, IgE antibodies aren’t released, and other parts of the immune system are used to fight the perceived threat.

Food allergy vs Food intolerance

Physical reactions to certain foods are common, but most are caused by a food intolerance rather than a food allergy. Many food intolerances are often mistaken for food allergies.

Food allergy

It causes an immune system reaction that affects numerous organs in the body. It can cause a range of symptoms. In some cases, an allergic food reaction can be severe or life-threatening.

Food intolerance

It can cause some of the same signs and symptoms as a food allergy, but it never involves the immune system. The symptoms are generally not life-threatening and often limited to digestive problems.

If you have a food intolerance, you may be able to eat small amounts of the offending food and to prevent a reaction. For example, if you have lactose intolerance, you might be able to drink lactose-free milk or take lactase enzyme pills (Lactaid) to aid digestion.

Causes of food intolerance:

  • Absence of an enzyme needed to fully digest a food: Ex. Lactose intolerance
  • Irritable bowel syndrome: This chronic condition can cause cramping, constipation, and diarrhea.
  • Sensitivity to food additives: Sulfites (used to preserve dried fruit, canned goods, and wine) can trigger asthma attacks in sensitive people.
  • Recurring stress or psychological factors: Occasionally the mere thought of food might make you sick. We don’t know the reason why.
  • Celiac disease: It has some features of a true food allergy because it involves the immune system. Symptoms: gastrointestinal issues, joint pain and headaches. However, people with celiac disease are not at risk of anaphylaxis. This chronic digestive condition is triggered by eating gluten, a protein found in wheat and other grains.

Diagnostic tests for Food Allergy

Allergy tests may help find allergies to things you eat, touch, or breathe in.

  • Dietary review: A detailed review of foods eaten, including timing and symptoms.
  • Blood tests: In some circumstances, blood will be drawn and the level of IgE antibodies measured.
  • Skin prick testing: A small amount of food is “pricked” into the skin using a tiny needle. The skin is then monitored for a reaction.
  • Oral food challenges: The offending food is eaten in a controlled environment under medical supervision in gradually increasing amounts.

However, allergy tests alone are generally not enough. Sometimes it can be difficult to tell food allergies and food intolerance apart.

If you suspect you have a food allergy or food intolerance, consult with your doctor to diagnose a food allergy instead of testing yourself. Your doctor may also refer you to a registered dietitian to manage your diet.

  • Allergy tests without a doctor’s exam, usually are not reliable
    The tests you can test at home may say you have an allergy when you do not (“false positive”) – not always reliable.
  • Unreliable test results can lead to unnecessary changes in your lifestyle
    If the test says you are allergic to some foods (though it could be false positive), you might stop eating those foods and end up with a poor diet, unnecessary worries or extra food costs. And tests for chronic hives (red, itchy, raised areas of the skin that last for more than 6 weeks) can show something that may not look normal but is not a problem. However, this can lead to anxiety, more tests, and referrals to specialists.
  • The wrong test can be a waste of money
    Allergy tests can be expensive. Skin test can cost $60 to $300, blood test can cost $200 to $1,000. A blood test for food allergies can cost hundreds of dollars, and test for chronic hives can cost thousands of dollars. Your health insurance may not cover the costs of these tests. And without a doctor’s exam, the test could be unreliable.

Food allergy symptoms

For people with a food allergy, even very small exposure to the offending food can cause an allergic reaction.

Symptoms of an allergic reaction usually occur anywhere from a few minutes to a few hours after exposure to food – mild to severe, affect various parts of the body, and occur in just one area of the body, or more than one area.

So be prepared in case you must treat an accidental exposure. Carry an auto-injector device containing epinephrine (adrenaline) and wear a medical alert bracelet or necklace.

You can prevent the symptoms only by avoiding the food. After you have identified the offending foods, you must remove them from your diet.

Mild symptoms

A mild reaction involves a mild symptom that affects only one area of the body.

  • Nose: itchy or runny nose, sneezing
  • Mouth: itchy mouth
  • Skin: a few hives, mild itch
  • Gut: mild nausea or discomfort

Severe symptoms

A severe reaction involves mild symptoms in more than one body area. Severe reactions can quickly progress to anaphylaxis (a serious allergic reaction that is sudden in onset and can cause death). For this reason, this must be treated with epinephrine.

  • Lung: shortness of breath, wheezing, repetitive cough
  • Heart: pale, blue, faint, weak pulse, dizzy
  • Throat: tight, hoarse, trouble breathing/swallowing
  • Mouth: significant swelling of the tongue or lips
  • Skin: many hives over body, widespread redness, swelling of face
  • Gut: repetitive vomiting or severe diarrhea
  • Psychological: feeling something bad is about to happen, anxiety, confusion.

10 Most Common Food Allergies

For adults: fish, shellfish, peanuts, and tree nuts
For children: eggs, milk, peanuts, tree nuts, soy, and wheat

1. Milk

It’s one of the most common allergies for babies and toddlers, especially when they have been exposed to cow’s milk protein before they are 6 months old. However, around 90% of children will outgrow it by 3 years old, making it much less common in adults.

Be aware of many processed foods since they often contain cow’s milk. The only treatment is to avoid cow’s milk and foods.

Many people make a mistake with a milk allergy for lactose intolerance since many of the symptoms are similar. See an allergist to determine the difference.

A cow’s milk allergy can occur in both IgE and non-IgE forms, but IgE cow milk allergies are the most common and potentially the most serious.

Children or adults with an IgE allergy tend to have a reaction within 5–30 minutes of ingesting cow’s milk. They experience symptoms like swelling, rashes, hives, vomiting and, in rare cases, anaphylaxis.

A non-IgE allergy usually has more gut-based symptoms like vomiting, constipation or diarrhea, as well as inflammation of the gut wall. It can be quite difficult to diagnose because the symptoms sometimes can suggest an intolerance and there is no blood test for it.

Breastfeeding mothers of babies with an allergy may also have to remove cow’s milk and foods that contain it from their own diets.

Foods That May Contain Milk Proteins

All dairy products contain milk, but so do some other foods. If you avoid milk due to allergy, you need to avoid milk proteins (casein and whey). These foods contain milk proteins:

  • Lactaid: This milk is designed for individuals with lactose intolerance, not a milk allergy. It contains milk protein but has had the milk sugar (lactose) removed.
  • Simplesse: This is a fat substitute made from egg and milk protein (whey) used in low-calorie food products like ice cream, yogurt, cheese spread, salad dressings, margarine, mayonnaise, coffee creamer, soups, and sauces. Simplesse is a trademark name so you may not find it listed by name as an ingredient. Instead, you may see “egg and milk protein,” “whey protein,” or “dairy protein.”
  • Dips and salad dressings: Any dips made with milk, yogurt or sour cream, such as ranch or blue cheese, may contain milk.
  • Non-dairy products: soy-, nut- or rice-based dairy products are manufactured on equipment shared with milk. Many of them contain casein.
  • Kefir: This fermented beverage is made from animal milk (usually cow’s milk) mixed with kefir grains. The result is a thick, smoothie-like drink. Most do contain milk protein.
  • Goat’s milk: While not identical to cow’s milk protein, goat’s milk and other animal-based milk like sheep’s milk have similar milk proteins and may cause an allergic reaction. It is recommended that milk-allergic individuals avoid other animal-based milk.

Milk and milk products that contain

  • Milk (in all forms: condensed, derivative, dry, evaporated, goat’s milk and milk from other animals, low-fat, malted, milkfat, non-fat, powder, protein, skimmed, solids, whole)
  • Milk protein hydrolysate
  • Buttermilk
  • Butter, butter fat, butter oil, butter acid, butter ester(s)
  • Casein, Casein hydrolysate, Rennet casein, Caseinates (in all forms)
  • Cheese
  • Cream
  • Curds
  • Custard
  • Diacetyl
  • Ghee
  • Half-and-half
  • Ice cream
  • Lactalbumin, lactalbumin phosphate
  • Lactoferrin
  • Lactose
  • Lactulose
  • Margarine
  • Pudding
  • Recaldent(R)
  • Sour cream, sour cream solids
  • Tagatose
  • Whey (in all forms)
  • Whey protein hydrolysate
  • Yogurt

Sweets that may contain milk

You probably realize that milk chocolate contains milk. But milk ingredients may be hidden in other sweets, including:

  • Caramel candies
  • Chocolate
  • Nougat: nougat is generally made with honey, sugar, nuts, egg whites, and possibly milk powder, although ingredients may vary. Always check the label for ingredients, or ask about them.
  • Chewing gum: Look for milk protein ingredients like Recaldent, which is made from casein and found in chewing gum brands such as Trident.
  • Sherbet: It is made with fruit, water, and sugar, but may also include egg whites, milk, or gelatin. Many brands of sherbet sold in grocery stores contain milk fat or cream. If you want a similar product, pick sorbet, which is made from fruit, water, and sugar. However, you always should check the ingredients.

Meat & seafood that may contain milk

Most people would not expect to find milk in meat products, but it’s actually a fairly common ingredient.

  • Luncheon meat: Deli meat slicers are often used for both meat and cheese products (cross-contact). Deli meats also may contain casein (milk protein) as a binder.
  • Hot dogs: Milk proteins may be added to hot dogs as an extender or filler, which allows the manufacturer to use less meat overall. Manufacturers of hot dogs are not required to list allergy ingredients since meats aren’t subject to the same allergen labeling rules as other products.
  • Shellfish: It is sometimes dipped in milk to reduce the fishy odor. Ask questions when buying shellfish.
  • Tuna fish: Some brands contain casein.
  • Steak: This is an issue in restaurants, not in the supermarket. Sometimes, a pat of butter to the top of a steak to make it look juicy. Ask for your steak “naked,” with no added ingredients, and ensure to alert your server of any food allergies whenever you are dining out.
  • Sausage: Similar to deli meats, milk protein may be used as a filler or binder in the processing of sausages like hard salami, Italian sausages or breakfast sausage.
  • Paté: Animal liver such as beef or chicken may be soaked in milk to remove blood (which gives an off taste) prior to the cooking, seasoning, and pureeing into a pate. Read ingredient labels.

Other possible milk sources

  • Artificial butter flavor
  • Baked goods
  • Lactic acid starter culture and other bacterial cultures
  • Nisin
  • Instant mashed potatoes: Read the ingredient label on your instant spuds, which are basically dehydrated potatoes. Some manufacturers add butter and/or milk before dehydrating the mixture so that the end result is a tastier product.
  • Medicine: Some medications contain milk protein like whey, so read the labels.

Milk in Kosher Foods

Kosher Dairy: “D” or the word “dairy” following the circled K or U on a product label means the product contains or is contaminated with milk protein. Avoid these products if you have a milk allergy.

Kosher Pareve: A food product labeled “pareve” is considered milk-free under kosher dietary law. However, a product may be considered pareve even if it contains a very small amount of milk protein—possibly enough to cause an allergic reaction in certain people. Don’t assume that these products will always be safe. 

Ingredients don’t contain milk protein and are safe to eat

  • Calcium lactate
  • Calcium stearoyl lactylate
  • Cocoa butter
  • Cream of tartar
  • Lactic acid (however, lactic acid starter culture may contain milk)
  • Oleoresin
  • Sodium lactate
  • Sodium stearoyl lactylate

Substitute: It’s best to follow an allergist’s advice. Oat milk is a great option since you can avoid both soy and nuts that are common allergy sources. Be careful of soy milk since soy allergies are common.

2. Eggs

An egg allergy is the second most common cause of food allergy in children. However, 68% of children with an egg allergy will outgrow it by the age of 16.

Interestingly, it’s possible to be allergic to egg whites, but not the yolks, and vice versa. However, egg white allergy is more common.

However, heating eggs can change the shape of the allergy-causing proteins, so some of you might not need to avoid all egg-related foods. In fact, one study found that around 70% of children with an egg allergy could tolerate eating biscuits or cakes with eggs. Some studies have also shown that introducing baked goods to children with an egg allergy can shorten the time it takes for them to outgrow the condition. Nevertheless, this isn’t the case for everybody, and the consequences of ingesting eggs when you are allergic to them can be severe. Check with your doctor first.

There is no cure or treatment for an egg allergy, though you can be regularly tested to see if your tolerance changes. Like other allergies, the treatment for an egg allergy is an egg-free diet.

Eggs are not always listed as “egg” on labels, so watch out for the terms: albumin, globulin, lecithin, livetin, lysozyme, words with “ova” and “ovo” as prefixes, silici albuminate, simplesse, and vitellin. These all imply that egg protein is present. These can even be in shampoo or other cosmetic products!

Substitute: Avoiding eggs while eating out can be tough, but egg-free cooking at home isn’t. Replace with cornstarch, flaxseed oil and tofu.

Symptoms include:

  • Digestive distress, such as a stomach ache
  • Skin reactions, such as hives or a rash
  • Respiratory problems
  • Anaphylaxis (which is rare)

3. Peanuts

We all love peanut butter, but peanut allergy is the most common food allergy in children under age 18 and the second-most common food allergy in adults.

While the reason people develop a peanut allergy isn’t known, studies showed that introducing peanuts early may be protective. Only about 20 % of children with peanut allergy outgrow it in their teenage years and can cause severe and fatal allergic reactions.

Let me remind you that a peanut is a legume, not a nut. Tree nuts (almonds, cashews etc.) grow on trees while peanuts grow underground and are part of the legume family. Nevertheless, those with peanut allergies are often also allergic to tree nuts.

Allergy to peanut is the only food allergy for which a treatment has been approved by the U.S. Food and Drug Administration.

If you realize that you’re allergic to peanuts, scrutinize the labels of any processed food or prepared meal. Whether you eat or inhale products cross-contaminated with peanuts, you could be susceptible to anaphylaxis. Cross-contamination is a big issue you need to watch out for.

4. Soy

Soy allergies are most commonly seen in infants and children under 3 years old. Interestingly, a small number of babies who are allergic to cow’s milk are also allergic to soy.

Soy allergies can be introduced through soy-based formula, and in this case, are often detected early. Soy can pop up in unexpected everyday foods: meat products, baked goods, chocolate, and cereals. So, it’s important to read food labels. Like other allergies, the only treatment for soy allergy is to avoid soy.

About 70% of children with the allergy outgrow the allergy. While some often leave this allergy behind in infancy, soy allergies carried into adulthood may be due to a family history of allergies like hay fever, asthma, hives, or eczema, you may be more susceptible to a soy allergy.

Substitute: lupin seeds are gluten-free, rich in amino acids and antioxidants, prebiotic, and low in fat and oil.

The symptoms: an itchy, tingly mouth and runny nose to a rash and asthma or breathing difficulties, in rare cases, anaphylaxis.

5. Wheat

The primary protein when allergic to wheat is gluten. Wheat allergies are very common but are often confused with celiac disease (a condition that prevents the body from absorbing proper nutrients and causes an adverse reaction to gluten) since they can have similar digestive symptoms.

Wheat allergy: Wheat allergy is most common in children and is usually most of them outgrow it by age 12. It causes an immune response to one of the hundreds of proteins found in wheat. This can be severe and sometimes fatal. People with a wheat allergy only need to avoid wheat and can tolerate gluten from grains that don’t contain wheat. It is often diagnosed through skin prick testing.

Celiac disease and non-celiac gluten sensitivity: they aren’t life-threatening. They are caused by an abnormal immune reaction to gluten. People with these must avoid wheat and other grains that contain the protein gluten.

It tends to affect children the most. Although, children with a wheat allergy often outgrow it by 10 years old.

Wheat products are hard to avoid: bread, pasta, crackers, and beer, etc. Sometimes severe reactions like anaphylaxis are triggered. Some who work with wheat flour may experience breathing problems, or “Baker’s Asthma,” from inhaling wheat allergens but experience no side effects when eating.

The only treatment is to avoid wheat and wheat-containing products: foods, beauty, and cosmetic products. This is how you can avoid it at home and in restaurants.

The symptoms: digestive distress, hives, vomiting, rashes, swelling, in severe cases, anaphylaxis.

Substitute: Gluten-free oats, rice flour, garbanzo bean flour, or even tapioca flour.

6. Tree Nuts

Tree nut allergies are very common and affect 1.2 % of the population. A tree nut allergy is an allergy to food products made with these nuts: almonds, macadamias, and tree nut oils, etc. Be careful since those could find in unexpected places like barbecue sauces, salad dressings, and even pie crusts.

Most common 6 tree nut allergies 

  • Almond
  • Cashew
  • Hazelnut
  • Pecan
  • Pistachios
  • Walnut

Allergies can also be very severe, and tree nut allergies are responsible for about 50% of anaphylaxis-related deaths. Unlike some other allergies, tree nuts allergy is usually a lifelong condition: most children who are allergic to one or more tree nuts don’t outgrow their tree nut allergy.

If you’re allergic to one of the nuts, you’re most likely allergic to a few of them. Avoid all types of tree nuts, even if they are only allergic to one or two types. You want to decrease your risk of developing an allergy to other types of tree nuts.

In addition, it might be best to avoid anything bearing the warning “may contain tree nuts” because there are numerous possibilities for exposure and cross-contamination to tree nuts. While many nuts are off-limits, pumpkin, sunflower, and sesame seeds are safe and often substituted in cooking.

7. Shellfish

Unlike many common food allergies, shellfish allergies are far more common in adults than children. A shellfish allergy doesn’t tend to outgrow over time, so most people with the condition must avoid all shellfish from their diet.

Crustaceans are easy to identify and avoid, but mollusks can often be mistaken as safe seafood to eat — squid and scallops among them. Some who suffer from shellfish allergies can eat certain types of mollusks, but others must cut them out completely.


  • Shrimp
  • Prawns
  • Crayfish
  • Lobster
  • Squid
  • Scallops

The most common trigger of a seafood allergy is a protein (“tropomyosin”). Other proteins are arginine kinase and myosin light chain. Interestingly, even the vapors from cooking shellfish can trigger a shellfish allergy in those who are allergic. Hence, avoid being around seafood when cooking seafood.

Symptoms of a shellfish allergy usually come on quickly and are similar to other IgE food allergies. However, a true seafood allergy can sometimes be hard to distinguish from an adverse reaction to a contaminant of seafood, such as bacteria, viruses or parasites. This is because the symptoms can be similar, as both can cause digestive issues like vomiting, diarrhea, and stomach pain.

8. Fish

Fish allergies are common, affecting up to about 2% of adults. Fish allergy can develop at any age. Unlike other allergies, 40% of people develop an allergy as an adult.

A fish allergy is not exactly the same as a seafood allergy. Seafood includes fish (tuna or cod) and shellfish (lobster or clams). Even though they both fall into the category of “seafood,” fish and shellfish are biologically different and don’t carry the same proteins. Hence, people who are allergic to shellfish may not be allergic to fish.

A fish allergy is sometimes confused for a reaction to a contaminant in fish (bacteria, viruses or toxins) because the symptoms can be similar. Finned fish (flounder, bass, and trout) can just as easily cause allergic reactions as shellfish. While the proteins in fish most often incite the immune system’s reactions, fish gelatin (in the bones and skin of fish) can be responsible for allergic side effects as well.

Symptoms: Like a shellfish allergy, a fish allergy can cause a serious and potentially fatal allergic reaction. Vomiting and diarrhea, but, in rare cases, anaphylaxis. Carry epi-pen in case accidentally eat fish.

Avoid seafood: seafood, Worcestershire sauce, Caesar salad dressing etc. Watch out for cross-contamination, especially in restaurants and other public places.

Many people with fish allergies are allergic to one or more types of fish. Though fresh fish is more likely to spur an allergic reaction, doctors generally recommend avoiding it entirely.

9. Raw Fruits and Vegetables

Some raw fruits like peach and vegetables like carrot contain the same proteins as some pollen – it is easy to develop oral allergy symptoms. While these are almost harmless compared to some other food allergies, they could cause anaphylaxis on rare occasions.

For some, simply peeling the skin of fruits and veggies reduces allergenic side effects. Also, cooking raw fruits and vegetables changes the shape of the offending proteins, which then causes no discomfort.

10. Sesame Seeds

The number of sesame seed allergies has grown in the U.S, but it’s not yet required for companies to put the warnings on food labels. As Middle Eastern foods (hummus, baked goods, sauces and dressings etc.) integrate into U.S. food culture, the sesame seed allergy rate will grow. Sesame seed allergy is the third most common allergy in Israeli children.

Allergic reactions to sesame seeds don’t necessarily mean allergies to other seeds. The likes of poppy, sunflower, and pumpkin seeds are generally not associated with allergic reactions and serve as fine substitutes

11. Other Foods

Less common food allergies can cause various symptoms from mild oral allergy syndrome to life-threatening anaphylaxis.

  • Aniseed
  • Avocado
  • Banana
  • Celery
  • Chamomile
  • Garlic
  • Kiwi fruit
  • Linseed
  • Passion fruit
  • Peach
  • Sesame seed
  • Mustard seeds



Epinephrine is a potentially life-saving device that can reverse the symptoms of anaphylaxis. It is available in an easy-to-use auto-injector (Auvi-Q ®, EpiPen® or Adrenaclick®).

Your allergist may prefer that epinephrine be used with only mild symptoms, or before symptoms even emerge. Consult with your doctor and refer to your personalized Food Allergy & Anaphylaxis Emergency Care Plan.

  1. Use epinephrine at the first sign of a severe allergic reaction, or as prescribed.
  2. Call 911. Tell the dispatchers that you have used epinephrine to treat a suspected anaphylactic reaction to food. Request an ambulance with epinephrine on board.
  3. Go to the emergency room for further treatment, even if symptoms appear to resolve with the epinephrine. The person may need more medication or treatment to manage the reaction.

Safety of Epinephrine

Epinephrine is a safe and relatively harmless drug. When in doubt, use it! The risks of anaphylaxis outweigh any risks from giving the medication.

Take extra caution only with patients for whom an increased heart rate could be a problem – elderly patients and those with known heart disease. But still use epinephrine to treat anaphylaxis in these people.


Steroids may be given, typically in the emergency room, to help reduce inflammation after an anaphylactic attack. They can be given orally (by mouth) or intravenously. Although steroids don’t work fast enough for emergency, they may help prevent a severe reaction from coming back.


Antihistamines (H1 or H2 blockers) are prescribed to relieve mild allergy symptoms affecting only one body area. An antihistamine cannot control a severe reaction and is no substitute for epinephrine. For anaphylaxis, many emergency departments give both H1 and H2 blockers.

H1 blockers: diphendydramine (Benadryl®), cetirizine (Zyrtec®) etc.
H2 blockers: Ranitidine (Zantec®) and famotidine (Pepcid®) etc.

Asthma medication

Short-acting bronchodilators (“rescue” inhalers) is used to help relieve asthma symptoms and other breathing problems once epinephrine has been given. One example of this medication is albuterol (Alupent®, Proventil®, Ventolin®). Asthma medications should not be used to treat the breathing problems during anaphylaxis – use the epinephrine.

Conclusion: Now you know the basic of food allergies. Be mindful of what you eat for you and your loved ones with the food allergy. 

If you find this blog post helpful, please help me out by sharing this blog post on your social media! If you have a tip to add or contents you’d like to see more on this blog, please feel free to leave a comment below.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.