Adult allergies

How to tell if you’ve developed an allergy as an adult?

By Dr Yusianmar Mariani, GP at London Doctors Clinic

As the most common chronic disease in Europe, allergies affect more than 20% of the populations of most developed countries. Out of these, one in five patients live with a severe debilitating allergy, and may fear the onset of an asthma attack, anaphylactic shock or even death from an allergic reaction (EAACI, 2016).

Over 21 million adults in the UK are affected by one or more allergic disorder.

In adults, the most common food allergies are peanuts, milk, eggs, tree nuts, shellfish, wheat and soy. Hay fever and eczema are also associated with increased food allergy risk.

Is it possible to develop an allergy in later life?

If you grew up allergy-free and thought you were immune for life, you might be disappointed. Adults can develop new allergies at any age. The onset age is between 18 and 86, and most patients have their first adult allergic reactions in their 30s.

There are different theories to explain this, one being that it is possible for a patient who’s never had exposure to a particular allergen, to develop an allergy to it.

But what causes the body to react to an allergen after many years of being in contact with it? The science behind these “late” reactions is still unknown. Some people may have experienced allergies earlier on life, without being diagnosed.

Another theory is the “hygiene hypothesis” which says that exposure to overly clean environments during childhood, makes people susceptible to developing allergies later on in life. This is because their immune systems don’t learn to fight against germs and infection.

Why does this happen?

Some people may have a family history which makes them prone to allergies in any case. Allergies develop when the immune system incorrectly identifies an everyday substance as harmful, such as pollen, mould, animal dander or food. The immune system then triggers a cascade of reactions to fight against the allergen, which causes symptoms such as wheezing, coughing, oedema etc.

When an allergen enters the body, the immune system produces antibodies, which are released into blood. An allergen-specific antibody can be carried by an adult throughout their life, without them knowing, and cause an allergic reaction at any time.

What are the most common signs that you are having an allergic reaction?

Have you ever struggled to shift a cough, had a constant itch in your nose or felt very bloated for sustained periods of time? If the answer is ‘yes’, you might have an undiagnosed allergy.

Symptoms could range from the standard sneezing, runny nose, itchy eyes, wheezing and coughing, to skin rashes (hives) or even anaphylaxis, which is a life-threatening allergic reaction and requires urgent medical assistance. 

When it comes to food allergies, patients may experience tummy pains, vomiting or diarrhoea. These would appear within a few seconds or minutes after eating the food although occasionally they can develop gradually over a few hours.

What should you do if you experience any of these symptoms?

Your first action should be to contact your GP so that you can be correctly diagnosed and treated.

While over-the counter antihistamines for mild allergies seem like a likely solution, they are not suitable for everyone. There are many treatment options available. For example, your doctor might prescribe decongestants for blocked noses, calamine lotion to reduce itchiness or steroids for inflammation. There are also many nasal sprays, eye drops, and topical creams available over the counter.

It’s not always practical, but where possible, the best way to prevent allergic symptoms is to avoid the allergen.

If you experience shortness of breath, a swollen tongue, tight chest, trouble swallowing or speaking and confusion, you should dial 999 and call an ambulance immediately, as these are symptoms of anaphylaxis.

How can you get tested and when should you seek medical attention?

Your GP will consult with you, and consider your clinical history, to help determine the best management and treatment options for you. The two most common ways to identify an allergy are:

  • Skin Prick test in which the skin in your forearm will be pricked with a lancet containing small quantities of the suspected allergens which will produce a local inflammatory reaction
  • A blood test for specific IgE test targeted against the suspected allergen(s)

Other methods include:

  • Elimination diet: your doctor might recommend cutting out a particular type of food

  • Challenge test: this is when you consume the food you suspect you may be allergic to, in gradually increasing amounts, and under close GP supervision
  • Patch tests: discs containing the allergens are taped into your skin for 48 hours

We discourage the use of commercial allergy-testing kits which are not reliable. Besides, it’s imperative that allergy tests are interpreted by a qualified professional - so if you suspect an allergy, go and see your doctor.