CPR First Aid

Can Food Allergy Reactions Happen After 12 Hours?

A food allergy can get in the way of the essential and enjoyable act of eating. Learn more about if food allergy reactions can happen after 12 hours.

Nutrients and sustenance are essential to everyone’s survival. People need to eat to get through the day. Food allergies, though, puts a damper on the crucial and enjoyable act of eating.

The good thing is that people can quickly tell which foods they are allergic to. Unfortunately, not everyone has the luxury to do this. This means that if they eat food they are allergic to, it may come as quite an unpleasant surprise.

The question we have before is, how long does a person have to wait for an allergic reaction to food to happen? Can food allergy reactions happen after 12 hours? Let’s find out together.

What Food Allergy Is?

A food allergy is when the body reacts to food it usually wouldn’t. This can be because the person lacks the enzymes needed to break down the food properly. It could also be due to an overreaction of the immune system where it sees the food protein as something harmful.

When this happens, it will release histamines and other chemicals to fight against this “intruder.” This causes people to react differently when they consume food they are allergic to.

At present, 2 in every 100 adults are diagnosed with food sensitivity.

Body reacts to unfamiliar food. Lack of enzymes or immune system overreaction sees food protein as harmful.

Most Common Allergy Foods

There are many common allergenic foods out there. The most well-known ones include:

  • Nuts such as peanuts, Brazil nuts, hazelnuts, almonds, macadamia nuts, cashews, and walnuts
  • Fish such as salmon, tuna, herring, and cod
  • Shellfish such as prawns, shrimp, crab, and lobster
  • Soya products
  • Dairy products such as milk and cheese
  • Eggs
  • Gluten found in wheat products
  • Fruit such as strawberries, kiwis, avocados, and bananas

If you aren’t quite sure if you are allergic to these foods, bear them in mind and be cautious when eating them.

The Difference With Food Intolerance

Food intolerances differ from food allergies because the former doesn’t cause an immune system reaction. This means that people who have food intolerances won’t have to worry about histamines being released.

The effects of food intolerances are also not as severe as food sensitivity or allergies. People who have food intolerances often experience bloating, gas, and stomach pain. They might also feel nauseous and get headaches. In more extreme cases, they could get diarrhoea and vomiting.

It should be noted that these allergies can also cause these symptoms. They can also lead to much more serious reactions such as anaphylaxis, a life-threatening condition.

Understanding the difference can help guide one’s actions when experiencing any of these.

Can Allergic Reactions to Food Happen After 12 Hours?

So, returning to the question, can food sensitivity reactions present themselves after 12 hours? The answer is, unfortunately, yes. People can experience allergic reactions or anaphylaxis, even 12 hours after consuming the food they are allergic to.

Why Does it Take That Long?

There are a few reasons why this might be the case. For one, food takes around 6-8 hours to make its way through the stomach and into the small intestine. This means that if you ate food you were allergic to 8 hours ago, there is a chance that your body is only now beginning to react to it.

Another reason is that some food allergens can be stored in your fat cells. This means that even if you stop consuming the food allergen, you might still react because your body constantly releases the allergen into your system.

The Common Symptoms of an Allergic Reaction After 12 Hours

What symptoms can one expect to experience if they have an allergic reaction after 12 hours? For the most part, they will be similar to the symptoms of a normal food allergy reaction.

"Allergic reaction symptoms after 12 hours: akin to food allergy symptoms."

Skin Reactions

One common reaction to allergies can be found on the skin. Several hives or welts will pop up on certain parts of the body. The swelling can extend to other parts, such as a person’s lips.

Apart from that, people will also have itchy sensations all over.

Mouth and Throat Problems

The mouth and throat are also prime targets for allergic reactions. This is because allergic foods pass through here.

A telltale sign of an allergic reaction is the tightening of the throat. Due to this, people will have a difficult time breathing. It can also hit the lungs, where problems such as wheezing and coughing come into the fray.

Digestive System Problems

Once the food hits the stomach, it also introduces a host of problems. It starts with stomach pains. Eventually, it leads to diarrhoea, nausea, and even vomiting.


Anaphylaxis is a potentially life-threatening reaction that can occur with food allergies. It is characterised by a sudden drop in blood pressure, constriction of the airways, and swelling of the lips, tongue, and throat. If not treated immediately, anaphylaxis can lead to death.

What To Do If You Have Eaten A Food You Are Allergic To

If you have eaten food you are allergic to, it is essential to seek medical attention immediately – even if you don’t think your reaction is severe.

Head to the Emergency Room

The best thing to do would be to go to the emergency room so that they can adequately monitor you and give you the necessary treatment.

If you cannot go to the emergency room, you can also call emergency services to come and pick you up if your symptoms keep you from heading over.

In the meantime, there are a few things that you can do to help ease your symptoms.

Tips to Ease Allergic Symptoms

If you are having trouble breathing, sit up straight and try to take deep breaths. This will help open up your airways.

If your throat is closing up, use an EpiPen if you have one. If you don’t have an EpiPen, then use a device such as an asthma inhaler or nebulizer.

If you are vomiting or have diarrhoea, drink clear fluids such as water or juices. You can also try sucking on ice chips.

Do not take any food or drinks until the medical professionals have cleared you.

Sit up, breathe deeply. EpiPen for closing throat.

React Fast to Bad Food Reactions

The bottom line is that allergic reactions to food can happen even 12 hours after consuming the allergen.

This is because food takes around 6-8 hours to make its way through the stomach and into the small intestine. Additionally, some food allergens can be stored in your fat cells and released into your system even if you stop consuming the food allergen.

With that said, it is also important to note that not all food allergy reaction times are the same. While 12 hours is possible, some can happen as fast as a few minutes. Other times, it can reach up to 24 hours.

The important thing is to react fast when an allergic reaction takes place. It may also help to learn about relevant first aid practices to help assist those experiencing it.

Learn more about relevant life-saving skills through CPR First Aid’s Liverpool courses today.

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