The Range of Allergic Reactions


Allergic reactions can range from mild skin or digestive issues to severe respiratory reactions and life-threatening anaphylaxis. Knowing if your child will or will not have a severe reaction to a food allergen on any particular day is unfortunately not possible. There are many factors that go into how severe a reaction is, but they are difficult to predict. It is important to remember that any child or adult with a food allergy of any type is at risk of experiencing anaphylaxis.

The Most Common Symptoms of Food Allergies are Not Severe

The good news for children with food allergies, and their parents, is that respiratory symptoms and anaphylaxis are not as common as other symptoms. The most common reactions involve skin issues, like hives, itchiness and dermatitis, or gastrointestinal issues, like cramps, vomiting and diarrhea. While these are uncomfortable, they are not life threatening.

Less common are respiratory symptoms with food allergies, including congestion, runny, itchy nose, asthma and swelling in the airways. These are more common with airborne allergens, like pollen. Those who experience respiratory symptoms from food allergens, or who have allergies and asthma, are at a greater risk of having a severe reaction, or anaphylaxis.

Another reason that most food allergy symptoms are mild is that oral allergy syndrome (OAS) is the most common type of food allergy. OAS mostly causes itchiness in the mouth and throat and sometimes a little bit of swelling of the lips, but rarely triggers a severe reaction. The reactions occur because the proteins in some foods are very similar to those in airborne pollen. Someone who has become sensitized to a type of pollen may then have an OAS reaction to certain foods.

One Person’s Reactions Can Vary

What can be so frustrating about food allergies is that it is nearly impossible to know when exposure will trigger a mild reaction or a severe reaction. Some people tend to have more mild reactions, but this does not indicate that they will never have a severe reaction. It is possible to go years with only mild symptoms and to then experience anaphylaxis, seemingly out of nowhere. There are some factors that can affect the severity of an individual’s reaction in a particular instance, or as compared to someone else with the same allergy:

  • People can have varying levels of sensitivity to the same allergen, and greater sensitivity generally causes more severe reactions.

  • People also have different thresholds. This is the amount of a food that they can eat before a reaction occurs. The more an individual eats above their own threshold, the more severe the reaction is likely to be.

  • Being sick can increase the severity of a reaction.

  • Some people have more severe reactions when they exercise.

  • Alcohol and some types of medications can also make an individual more sensitive to their allergen.


It’s not fully understood why some of these factors impact the severity of an allergic reaction. It may be that certain factors increase the action of the immune system or affect the digestion of a food, slowing or speeding the absorption of an allergen into the bloodstream.

Risk Factors for Severe Allergic Reactions

It isn’t possible to predict who will have anaphylaxis as a result of exposure to an allergen, but there are some risk factors that make it more likely. Food allergens are more likely to cause this severe reaction than other types of allergens, like pollen or dander. Anyone with a food allergy is considered to be at risk for anaphylaxis. Other risk factors for a severe reaction include having asthma, especially asthma and a food allergy, and having certain other health conditions like heart disease or mastocytosis.

An important risk factor for anyone with an allergy is already having experienced anaphylaxis. A previous incident makes someone more likely to have a severe reaction again, sometimes very soon after the first. Called biphasic anaphylaxis, anywhere between one and 20 percent of people who have anaphylaxis will have an episode again, within hours. A recent study found that in most children who had this biphasic experience, the second reaction occurred within six hours of the initial reaction.

Always be prepared to respond to anaphylaxis if you or your child is allergic to one or more foods. In spite of everything that is known about the severity of reactions, there is just no way to know for sure who will have a life-threatening episode or when.