9.FEB.2021 5 MIN READ | 5 MIN READ

Your gut does a lot more than digest your meal, it also influences whether we develop food allergies or intolerances during adulthood.

Last updated on 1 December 2021

We hear a lot about children having food allergies, but did you know that it’s possible to develop food allergies at any age? While it’s not clear why this happens, it is possible for adults to develop an allergy to foods that they previously had no problems with.

While children may outgrow their food allergies, that’s very unlikely to happen in adults hence adults won’t be able to count on the passage of time to shake off common food allergy triggers such as peanuts, fish, shellfish (prawns and crabs), and tree nuts like almonds, walnuts and cashews.

Symptoms of food allergies

The symptoms of food allergies in adults are similar to that in children, and reactions can happen quickly, within minutes, or hours later . These symptoms can range from mild to severe and may include:

  • Tingling of the mouth
  • Swelling of the lips, face, tongue or throat
  • Hives
  • Diarrhoea
  • Vomiting
  • Trouble breathing

Differences between food allergy and intolerance

Allergy vs intolerance
Most physical reactions to food are actually food intolerances but because food intolerance and food allergies have similar signs and symptoms, these two are often confused.

Food intolerance

Food intolerance is usually less serious and is mostly limited to digestive issues such as stomach aches, cramps, and diarrhoea.

Food allergies

Food allergies cause an immune system response that involves multiple organs in the body and can become life-threatening.


Those with severe food allergies may find themselves at risk of anaphylaxis, a potentially life-threatening allergic reaction. In anaphylaxis, your immune system overreacts, causing a full-body allergic reaction with symptoms such as:

  • Swelling of the throat
  • Weakness or dizziness
  • Rapid or abnormal heart rate
  • Facial swelling
  • Hives
  • Low blood pressure
  • Wheezing

Anaphylactic shock is when someone stops breathing or experiences airway blockage due to the airways being inflamed. This could also lead to a heart attack. Those who have experienced or are at risk of anaphylaxis should carry an emergency epinephrine (EpiPen) shot in the event of a severe allergic reaction.

Learn how to be prepared if your child goes into anaphylactic shock.

Gut microbiome and allergies

Your gut contains trillions of bacteria, viruses, fungi, and other tiny living organisms. Collectively, these are known as gut microbiota or flora, which help to regulate many important functions in your body that keep us healthy, such as helping to keep your immune system healthy by supporting communication with lymphocytes, the cells of your immune system.

Healthy people have high diversity in their gut microbiota, with studies showing that healthy people tend to have greater diversity of gut bacteria compared to those who are frail, or suffering from conditions like obesity, diabetes, atherosclerosis (clogged arteries), and eczema. Adults with allergies have also been shown to have a lower degree of gut bacterial diversity.

Developing food allergies as an adult

Generally, a person experiences food allergies when their immune system reacts towards certain food proteins as a threat. This causes the body to release certain chemicals in response, which result in the symptoms of food allergies. Common food allergies in adults include peanuts, fish, shellfish and tree nuts.

Increased use of antibiotics

The increased use of antibiotics – prescribed for the treatment of infections, and also present in the meat we eat – reduces our gut bacterial diversity and may be a reason why some people may not have the immune defences to prevent allergies. This is because antibiotics are well-known for disrupting the healthy bacteria and fungi that live in the gut.

Modern sanitation

Modern sanitation reduces the array of different bacteria we’re exposed to and this makes our gut flora less diverse. This may lead to our immune system reacting to things that should be harmless and causing an allergic reaction.

Immune system weakens with age

As we age, the immune system undergoes changes and declines, which impacts our health. This weakening of the immune system increases our risk of bacterial and viral infection and could also upset the balance of our gut flora. Reduced bacterial diversity in the gut has also been related to inflammatory bowel disease, a disease caused by an abnormal gut immune system.

Maintaining a healthy digestive system

Healthy digestive system

Improving gut health

Our digestive system ages along with us and common issues that can crop up include constipation and slowing down of the digestion process. Constipation can be caused by medication, inactivity, and reduced intake of water.

As there might be a relationship between your gut health and allergies to food during adulthood, it is important to maintain a healthy digestive system. This includes a balanced gut flora and ensuring that you have more good bacteria than bad bacteria in your gut. Things that could throw off your gut flora include having a diet high in sugar and fat and low in fibre.

Food to improve gut health

This is why eating a balanced diet with plenty of fruits and vegetables, whole grains, legumes, and beans, may help to maintain a balanced gut flora. A diet high in fibre also helps prevent constipation. Fermented food such as yoghurt and kimchi contain healthy bacteria called Lactobacilli which could help reduce harmful bacteria in the gut.

Cutting down on your sugar intake lowers your blood sugar levels, which is beneficial because high levels of blood sugar may encourage the growth of bad bacteria.

Do note that we’re not against taking the antibiotics prescribed by your doctor as they are a great way to fight bacterial infections. But as they are known to disrupt the gut flora, it’s imperative that you finish any course of prescribed antibiotics as advised by your doctor, and at the same time, keep eating healthily in order to rebalance your gut flora.

If you’ve had a reaction to food that you normally eat, there’s a possibility that it’s gut related. Don’t suffer in silence and do see a gastroenterologist who can help you with your tummy troubles, suggest ways to help better your digestive system, and prevent more food intolerances or allergies.


Article reviewed by Dr Wang Yu Tien, gastroenterologist at Gleneagles Hospital


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Wang Yu Tien
Mount Elizabeth Hospital