Have you heard of the term sensitisation? It’s especially used in connection with allergy tests that identify allergy triggers by detecting your sensitisation to specific allergens. But what is sensitisation and how is it different to allergy? In this article we’re going to explain the process of how allergy develops. We’ll also explain the difference between sensitisation and allergy, and the role sensitisation plays in allergy testing.What is allergy?To understand sensitisation we need to take a closer look at the mechanics of allergy. Allergy is an overreaction of your immune system in response to a substance that is normally harmless.Substances that cause allergic reactions are called allergens. If you have allergy your immune system mistakes the allergen as a threat and overreacts to try to protect you.There are many types of allergies. You can read more about the different types of allergy here. What happens when you have an allergic reaction? In an allergic reaction to substances such as pollen, house dust mites, certain foods or insect stings, the immune system produces antibodies called Immunoglobulin E (IgE) specific to the trigger it’s trying to fight.These IgE antibodies tell other cells to release certain chemicals, including histamine. And it’s those chemicals that cause the annoying and sometimes even life-threatening allergy symptoms.What is sensitisation then?Sensitisation is the first step of developing allergy.Allergic reactions don’t happen the first time you encounter an allergen. To begin with, your immune system has to meet the allergen. For example, by being stung by a bee. Then your immune system memorises the particular structure of the allergen so that it can produce specific IgE antibodies in defence. This process is called sensitisation.You’re sensitised when you have specific IgE antibodies in your blood. Once you have been sensitised to a particular allergen, your body will produce IgE every time you encounter that allergen again.When does sensitisation usually develop?Sensitisation happens early in childhood and without you being aware of it. The production of IgE begins when a baby is still in the womb. Sensitisation to foods like eggs and milk can happen when a baby is a few weeks to a few months old. Sensitisation to other allergens in the environment such as pollen, house dust mites and pets takes a bit more time to develop and usually happens in the pre-school or early school years.Can you be sensitised to more than one allergen?Sensitisation to more than one allergen is common, affecting 10% of the general population and more than half the people with allergy. Being sensitised to just one allergen is sometimes called monosensitisation. But you can also be sensitised to multiple allergens. This is known as polysensitisation.No allergy without symptomsSensitisation is not the same as allergy. Sensitisation does not always lead to symptoms, but symptoms do not develop without sensitisation. In other words, you can be sensitised without being allergic, but you can’t be allergic without being sensitised first.Sensitised but not allergicSome people have developed IgE antibodies for a specific allergen but when they come into contact with that trigger again, they don’t experience any allergy symptoms. These people are sensitised but not allergic. In other words, their immune system is sensitive to an allergen or allergens, but they don’t experience any symptoms of allergy.Sensitised and allergicFor other people, when they are re-exposed to the allergen, they experience allergy symptoms. These people are both sensitised and allergic. Their immune system is sensitive to an allergen or allergens, and this causes symptoms of allergy.Why are some people just sensitised and others allergic?We aren’t sure why some people stop at sensitisation and others progress to allergy. Our immune systems are highly complex and not all processes and mechanisms are fully understood yet.We do know that you are more likely to develop an allergy if other members of your family also have allergy. This doesn’t mean that you inherit a particular allergy, it means you may inherit the tendency towards having allergy. But there’s always an exception, some people have allergies even if no family member does.Allergy tests show your sensitisation to specific allergensBecause it’s possible to detect sensitisation, it can be a useful tool for identifying potential allergy triggers. Testing for IgE can give you an indication of your sensitisation to specific allergens.So, results of a test for sensitisation can be a first step to finding out if you have an allergy.It’s important to remember though that an accurate diagnosis of allergy requires both a test and a consultation with your doctor. Your medical history is the fundamental link between your allergy test results and being diagnosed with allergy. Only a doctor can give you a diagnosis of allergy and access to the whole range of allergy management options.klarify.me - We’re here for youWe have a wealth of further information available for you in the Allergy Know-how area of our website. Find everything you need to know about allergies in our easy-to-read, research-based articles.Discover tips and practical solutions to help reduce the impact of allergies on your life. We make life with allergy surprisingly simple.Thank youIf you’ve read all the way to the end of this article, thank you. 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