Last updated: 15.09.22

What to Do if Someone has a Food-based Allergic Reaction

Food allergies affect a significant proportion of the population. In the UK, 20% of people have one or more allergic disorders, many of which are an allergy to a particular ingredient. (Source)

Those suffering from food allergies need to be careful whenever they’re shopping for food or eating out at restaurants, particularly if they’re at risk of a severe allergic reaction. But it’s also the responsibility of those that own or work in a food establishment to be aware of the risks that certain ingredients present to consumers and what to do if someone has an unexpected allergic reaction.

As a business, you should provide consumers with as much information about potential allergens as possible to avoid incidents like customers going into anaphylactic shock or experiencing even mild symptoms of a food allergy. Listing allergens on any food packaging or menus is essential to letting consumers know what dishes contain allergens and gives them the best chance at avoiding triggers. 

Keeping your kitchen in good working order with adequate control measures to identify and separate potential allergenic ingredients is also imperative.

Despite this, you should still prepare for the chance that a customer might have an allergic reaction whilst visiting your business. Knowing the signs of an allergic reaction and how to respond can prevent serious harm to the person suffering from allergies, which can be helpful in a wide range of scenarios, not just whilst you’re at work.

In this article, we explain what causes an allergic reaction, the main severe allergic reaction symptoms and what to do if someone has an allergy attack.

What Is an Allergic Reaction?

An allergic reaction is what happens when someone ingests food that their body is allergic to. It is caused by the body’s immune system reacting to certain proteins in food products as if they were a pathogen, producing chemicals to try and fight the ‘harmful’ substance which triggers allergic reaction symptoms.

Allergic reactions can range quite dramatically in severity, from a slightly irritating rash on the skin to a life-threatening anaphylactic shock. The latter is a much less common response than the former, but also needs immediate medical attention which is why it’s important to understand what an allergic reaction can look like and how you should respond.

What Can Cause an Allergic Reaction?

People with allergies can be allergic to a wide range of different substances and ingredients. However, there are 14 main allergens that are the most common, which are listed below:

  • Celery
  • Cereals containing gluten, like wheat, rye, barley and oats
  • Crustaceans, like crab, lobster, prawns and scampi
  • Eggs
  • Fish
  • Lupin
  • Molluscs
  • Mustard
  • Nuts, usually cashew nuts, almonds and hazelnuts
  • Peanuts
  • Sesame seeds
  • Soya
  • Sulphites (Sulphur Dioxide), often found within dried fruits, some meat products, soft drinks and alcoholic beverages

What Does an Allergic Reaction Look Like?

The range of symptoms that can indicate an allergic reaction is quite varied. The kind of food allergy will also determine how quickly symptoms present; IgE-mediated food allergies trigger symptoms that occur very quickly after coming into contact with an allergen, whereas non-IgE-mediated food allergies cause much slower reactions that may take days to appear.

If someone is having an IgE-mediated allergic reaction, their symptoms might involve:

  • Red and itchy rashes or hives on the skin
  • Swelling, usually on the face and around the mouth
  • Itchy eyes
  • Tingling around and in the mouth, often concentrated on the gums
  • A swollen throat, making swallowing difficult
  • Breathing difficulties and wheezing
  • Sneezing
  • Feeling short of breath
  • Feeling dizzy
  • Nausea
  • Abdominal pain
  • Diarrhoea

Many of these symptoms can overlap with the symptoms of a non-IgE-mediated allergic reaction. This kind of delayed allergic reaction might also involve:

  • Pale skin
  • Heartburn
  • Indigestion
  • Constipation
  • Loose or bloody stools
  • A rash or redness around the anus or genitals

In serious cases, an allergic reaction to a food allergen, whether that’s one of the 14 most common allergens or otherwise, can result in anaphylaxis. This means that the affected person can go into anaphylactic shock, which is a very serious reaction that requires urgent medical attention.

The symptoms of anaphylaxis are:

  • Feeling lightheaded or faint
  • Difficulty breathing, taking shallow breaths
  • Wheezing
  • Having an increased heart rate
  • Clammy palms or skin
  • Breaking out in hives
  • Nausea, stomach pain or vomiting
  • Confusion and anxiety
  • Loss of consciousness

Anaphylaxis can kill if it isn’t responded to and treated quickly, so understanding first aid for anaphylaxis is very important, particularly if you work in an environment where allergens are present. This can help you respond quickly and avoid symptoms from escalating by providing assistance and contacting the emergency services.

How to Treat an Allergic Reaction

Mild allergic reactions to food don’t usually require professional medical intervention, as the symptoms aren’t dangerous and won’t escalate. Most mild reactions can be treated with an over-the-counter antihistamine, which makes symptoms more manageable until the allergic reaction stops happening.

A serious allergic reaction (anaphylaxis) does require proper treatment however, 

First of all, you should contact emergency services immediately if you know that someone has had a reaction to a food allergen and gone into anaphylactic shock. As mentioned previously, Anaphylaxis is listed as a medical emergency and can escalate if not treated quickly, resulting in serious complications.

Next, determine whether an adrenaline auto-injector is nearby and needed. These narrow blood vessels and counteract the effect of low blood pressure, which can help to reduce breathing difficulties during anaphylaxis and keep someone alive and in a stable condition whilst they wait for medical help.

Adrenaline auto-injectors, such as EpiPens and Jext, are a useful measure to have in a business first aid kit, just in case. However, customers with food allergies may also carry around a personal one, especially if they have moderate to severe allergies. You should only attempt to do this if you know how to use it correctly or can assist someone who does.

Different kinds of adrenaline auto-injector work differently, but in most cases, you should remove the safety cap at the bottom and then press the injector firmly into the outer thigh of the person having a bad allergic reaction. Listen for a ‘click’, wait for ten seconds and then remove the injector, massaging the area for a further ten seconds.

After adrenaline has been administered, you should remove any triggers that you are able to without making the situation worse. Lie the person experiencing the allergic reaction down flat (unless unconscious, pregnant or have breathing difficulties), as this can make their symptoms more manageable.

Most people with food allergies carry two adrenaline auto-injectors with them. If you’re still waiting for medical help to arrive after 5-15 minutes and the sufferer’s symptoms are not improving, you should give them a second injection.

In some cases, anaphylactic shock can lead to unconsciousness. If the person is unconscious, they should be placed in the recovery position to keep their airway open and clear so that breathing is as easy as possible in their condition. 

Pregnant women should be laid on their left side to avoid putting excess pressure on the large vein which leads to the heart, and those with breathing difficulties should be kept upright.

If the person suffering from anaphylaxis stops breathing or their heart stops then CPR (cardiopulmonary resuscitation) should be performed immediately by someone who is first aid trained. This should continue until the emergency services arrive to ensure the person is kept in a stable condition.

If you own a food business that handles and sells products containing allergens, ensure staff know what to do if a customer goes into anaphylactic shock and are trained to handle the situation effectively and efficiently. For more information, we also have a video resource on what to do if someone is having an allergic reaction.


How long does it take to have an allergic reaction?

The majority of serious allergic reactions happen very quickly and can take anything from several seconds to a couple of minutes after initial exposure to occur. However, non-IgE-mediated food allergies cause reactions that usually take place several hours after the allergen has been consumed, and in rare cases may only trigger symptoms a full day after initial exposure.

How long does an allergic reaction last?

The length of an allergic reaction really depends on its severity and the symptoms. Some people can take several days to feel completely normal even after suffering from a mild allergic reaction to food, whilst others will find that their symptoms pass quite quickly, especially if antihistamine medication is taken.

Anaphylaxis is quite a rapid allergic reaction that usually only lasts for around 30 minutes, but in very severe cases could take days to properly subside. Recovery from this kind of reaction will often take longer as well, as the body will have been put under a lot of stress.

What does an allergic reaction rash look like?

Different allergens cause different kinds of rashes. A classic rash caused by an allergic reaction will usually involve hives on the skin, which are swollen red blotches that feel itchy and hot. Some people may react to allergens with a rash that looks like little red dots, whereas others may find that they develop eczema or that existing eczema symptoms get worse.


Those that work with allergens in a food preparation environment might just think that their responsibilities involve keeping allergens separate and correctly labelling ingredients. But understanding what to do if an allergen triggers a reaction is also important, especially if you work in an environment where food is served and consumed, which is why many workplace health and safety courses now cover the signs of an allergic reaction and how to treat anaphylaxis.

If you want more information on responding to allergic reactions to food, Virtual College offers an online ’Food Allergy Awareness Training Course’ which contains all the relevant information your staff will need to keep consumers safe, combined with best practice methods to ensure they know where essential allergen information on your products should be kept.