Not all allergies appear from a young age. It’s possible to develop them in later life, and the symptoms might not always be obvious. Here are the signs you need to look out for.
Words: Amy Mica Marsden. Images: Shutterstock.
Dangerous allergic reactions accounted for more than 25,000 NHS hospital stays a year in 2022/23, with the number thought to be growing more each year.
But not all allergic reactions are so severe – in fact, many might fly under the radar.
It’s thought that up to 10% of adults develop an allergy after the age of 18, and for many, it happens suddenly and without warning.
But what are the types of allergy, and how can we figure out what’s causing our symptoms?
Types of allergy
Food allergies are generally divided into three categories:
IgE-mediated food allergy
These are the most common types, triggering a near-immediate reaction. Symptoms can range from mild to severe and may include skin reactions, respiratory symptoms, facial swelling, or, in some more serious cases, anaphylaxis.
Non-IgE-mediated food allergies
These allergies tend to be harder to spot, as they have a delayed onset. By the time you’re experiencing symptoms, it’s harder to know what caused them, as exposure to the allergen might have happened a few hours beforehand or even in the preceding days.
Mixed IgE and non-IgE-mediated food allergies
Some people with a mixed food allergy might experience a combination of immediate and delayed symptoms.
Allergic reactions happen when the immune system overreacts to an otherwise harmless substance (allergen) and tries to protect you from the new ‘threat’.
To do this, the body releases antibodies called immunoglobulin E (IgE), which bind to the cells and cause the release of chemicals, which in turn cause allergic symptoms.
‘When people have an immediate allergic reaction to a specific food they are allergic to, we class the reactions as mild/moderate or anaphylaxis (potentially life-threatening),’ says Anne Biggs, deputy head of clinical services at Allergy UK.
‘Even though most reactions that occur are mild, all immediate-type (IgE-mediated) food allergies have the potential to result in a severe, life-threatening reaction.’
Anne noted that the severity of an immediate-type reaction depends entirely on the circumstances the person is experiencing at the time.
For example, illness, exercise, alcohol, sleep deprivation, menstruation, and certain medications can lead to a reaction becoming more severe than previously experienced.
Immediate allergy symptoms
According to AllergyUK.org, symptoms of an immediate (IgE-mediated food allergy) may include ‘skin reactions (such as itching, hives, or eczema), digestive issues (like vomiting, diarrhoea, or abdominal pain), respiratory symptoms (such as coughing, wheezing, or difficulty breathing), swelling of the lips, tongue, throat, or face, and in severe cases, anaphylaxis’.
If you or anyone you know experiences any of these symptoms very soon after eating, it’s important to seek medical attention.
For example, the NHS recommends calling 999 if your lips, mouth, throat or tongue become severely swollen; if you’re breathing fast or struggling to breathe; if your throat feels tight or you’re struggling to swallow; if your skin, tongue or lips turn blue, grey or pale; if you become confused or dizzy, or if fainting occurs. Find out more here.
Delayed-type allergy symptoms
However, delayed-type (non-IgE-mediated) allergies may not be as obvious – you may not even realise you have an allergy in the first place.
‘The most common food allergy in the adult population is pollen food syndrome (PFS), which usually causes mild symptoms,’ says Anne.
This allergy, also known as ‘oral allergy syndrome’, is a ‘hypersensitivity reaction to fruits, vegetables and nuts (often referred to as plant-based foods)’, and usually causes mild symptoms such as itchy mouth, lips or throat when the foods are eaten in their raw form.
PFS is relatively common, affecting around 2% of the population – and it’s especially common if you also suffer from hayfever or asthma.
Other delayed-type allergies which may be missed include allergies to milk and soya, as well as some other, much rarer types (such as a reaction to meat after a tick bite).
Common symptoms of delayed-type allergies include abdominal discomfort, vomiting and diarrhea, and can take several hours or even days to appear. You may also experience symptoms such as bloating, headaches or fatigue, and these symptoms often go overlooked for years without realising the cause.
These are not to be confused with food intolerances, which usually give digestive discomfort but don’t involve the immune system response that allergies cause.
What to do if you suspect you’re allergic
‘Understanding the food someone is allergic to, accessing support and advice from your clinical team on the food allergy and how to manage it is really important,’ advises Anne.
‘Food allergy can be complicated, with some people being able to safely eat a certain amount of a form of a food. The advice will vary from person to person, and a dedicated allergy team or dietitian is vital in supporting and advising on a case-by-case basis.’
