CPR First Aid

Can Food Allergy Reactions Happen After 12 Hours

Can Food Allergy Reactions Happen After 12 Hours?

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

The good thing is that people are easily able to tell which foods they are allergic to. Unfortunately, not everyone has the luxury to do this. This means that if they eat food that 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 the allergic reaction take place after 12 hours? Let’s find out together.

What Food Allergy Is?

A food allergy is when the body has a reaction to a food that it normally 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 in order to fight against this “intruder”. This is what causes people to have different reactions when they consume food they are allergic to.

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

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 which is found in wheat products
  • Fruit such as strawberries, kiwis, avocados, and bananas

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

The Difference With Food Intolerance

Food intolerances are different from food allergies in the sense that 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 which is 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, coming back to the question at hand, can food sensitivity reactions present themselves after 12 hours? The answer is, unfortunately, yes. It is possible for people to experience allergic reactions, or anaphylaxis, even 12 hours after they have consumed 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, it takes around 6-8 hours for food 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 actually be stored in your fat cells. This means that even if you stop consuming the food allergen, you might still have reactions because your body is constantly releasing the allergen into your system.

The Common Symptoms of an Allergic Reaction After 12 Hours

What are the symptoms that one can 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.

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 even 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 due to the fact that 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 very hard 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 off 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 important 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 properly monitor you and give you the necessary treatment.

If you are unable to go to the emergency room, you can also call emergency services to come and pick you up if your symptoms are keeping 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.

React Fast to Bad Food Reactions

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

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

With that said though, it is also important to note that not all food allergy reaction times are the same. While 12 hours is possible, some of them 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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