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Signs You're Allergic to What You Just Ate

The ugly and immediate side effects of a food allergy.
FACT CHECKED BY Samantha Boesch

It is estimated that 32 million Americans have food allergies, with the most common ones being shellfish, milk, and peanuts. And while it is true that most allergies appear during childhood, noticing allergy-related symptoms after the age of 18 does still happen. As a result of immune responses that cause negative reactions once a food is eaten, a food allergy can manifest in many ways.

To determine whether you are allergic to what you just ate, the first step is to understand the difference between a food allergy and a food intolerance. A food intolerance means that your body does not tolerate a certain food. In situations like a lactose intolerance, a person is not able to tolerate the lactose sugar found in dairy foods. Eating it may cause major discomfort, diarrhea, and bloating. But, unlike an allergy, it is not life-threatening.

Allergies, on the other hand, cause your body to react to a protein via an immune response. So, unlike an intolerance like lactose intolerance, having a true cow's milk protein allergy can trigger more life-threatening reactions.

So, if you ate a food and you are experiencing a surprising (or scary) reaction, how do you know if you have a true allergy? To truly determine whether you are allergic to a certain food, a doctor will have to perform tests to give you a proper diagnosis. But, experiencing some outcomes may be a sign that you should pay your doctor a visit for further investigation.

If you are curious to understand which signs to look out for that may indicate you are allergic to what you just ate, read on to learn five that you should have on your radar.

Then, for more allergy-related tips check out The Alarming Reason Why So Many People Have Food Allergies.


Developing itchy welts after you eat a certain food may be an indication that you have a food allergy. Typically looking like raised pink bumps that look similar to bug bites, seeing hives within minutes to a couple of hours of eating a food may mean that you should call your doctor to get evaluated.

Tight Throat and Trouble Swallowing

If your throat begins to swell and you are having a hard time swallowing, you may be allergic to a food that you ate. Inflammation of the esophagus can occur due to exposure, which can make it hard to swallow.


When a protein is labeled as "foreign" by the body and an allergic reaction is triggered, histamine is released. This compound can lead to constriction in the airways, causing a person to wheeze.


Vomiting can be a sign of a food allergy, although it can also be an indication of food intolerance or food poisoning. If you are vomiting, it can be difficult to know if this symptom is due to an allergy or intolerance, so it will be best to consult with your healthcare provider to get to the bottom of it.

 The Ugly Side Effects of Seasonal Allergies, Expert Says

Swollen tongue

Seeing your tongue swell can be more frightening than dangerous, although in some cases, the swelling may affect swallowing abilities. Typically, tongues go back to their normal size. But experiencing this reaction makes it worth contacting your doctor to determine whether there is a larger cause for concern.


Anaphylaxis is a severe and potentially life-threatening reaction to being exposed to an allergen. A person experiencing this may have trouble swallowing or breathing, have a faster heartbeat, and they may even lose consciousness in extreme cases. An EpiPen is used to treat this symptom, and if a person experiences it, they should absolutely speak to their health care provider.

Lauren Manaker MS, RDN, LD, CLEC
Lauren Manaker is an award-winning registered dietitian, book author, and recipe developer who has been in practice for almost 20 years. Read more about Lauren