An allergy occurs when a person’s immune system over-reacts to something in the environment that would be a harmless encounter for most other people. Common allergic reactions occur in response to exposure to things like pollen, house dust, animal dander, insect stings, food and some medications. These allergic reactions can be strong and immediate and may even be life-threatening.
Symptoms of an allergic reaction
The symptoms of allergy depend on which part of the body is affected by the immune response, whether that is skin, nose, lung, gastrointestinal tract or any other area. So, common symptoms might include:
skin – raised, red, itchy rash or hives
nose – blocked, runny and itchy nose, sneezing
eyes – red, watery and itchy eyes
lungs – cough, wheezing and shortness of breath
face – itchy and swollen face, lips, tongue or throat
stomach – nausea, abdominal pain, diarrhoea
These symptoms are caused by the release of histamine by certain cells in the body. It is also possible to have symptoms due to too much histamine in the body, even without having an allergy. See Do you have allergies? Or, is it histamine intolerance…
Food allergy is not the same as food intolerance, to learn the difference read Food allergy and food intolerance – a quick guide
How to avoid an allergic reaction
An allergic reaction occurs in response to contact with a substance to which you are hypersensitive. So the most effective way to avoid an allergic reaction is to avoid contact with the substance to which you are allergic, if possible.
Of course if you don’t know what that substance is then that can be a problem. You can take steps to find out, either through testing such as skin prick testing. Or, by keeping a diary of symptoms and trying to work through things systematically until the substance is identified.
However, in many cases a person is allergic to more than one substance, and of course this makes it more difficult to both identify and avoid the allergen – the substance that triggers your allergy.
What is atopy?
Atopy is the inherited tendency to be susceptible to developing allergies. Atopy gives rise to conditions in people, such as atopic eczema, allergic rhinitis, allergic conjunctivitis, allergic asthma and food allergy.
Although atopic people usually have a family history of allergy, we know that genetic bad luck is not the whole story, since identical twins have the same genes but do not always have the same tendency to allergies.
So, as is the case with many inherited conditions, having certain genes does not mean development of the associated condition is inevitable. It is in fact the interaction between your genes and the environment that has the main influence. The factors that we are exposed to can switch on or switch off the genes that make us vulnerable to particular health conditions.
The hygiene hypothesis
In fact there is an theory that the factors we are not exposed to may be just as important, or perhaps more important in the development of allergies. Children with older siblings, or that grew up in a household with pets, or on a farm are less likely to develop allergies. This fact has given rise to the hygiene hypothesis, and the idea that living in an environment that is less abundant in a wide variety of microbes provides less challenge to the child’s immune system and predisposes them to allergy development.
The immune system and the allergic response
An allergic response occurs when an allergen binds to IgE antibodies attached to mast cells. The binding immediately activates the mast cell which sends out chemical signals and creates a cascade of events that result in the symptoms of allergy. Part of this process involves the activation and differentiation of a type of blood cell called T helper cells. There are several different types of T helper (Th) cells and researchers believe that it is the balance of the different types that plays an important role in the susceptibility to allergies.
People that have a greater preponderance of Th type 2 (Th2) cells compared to Th1 cells are more susceptible to allergies. In addition there are regulatory T cells (Tregs) that may have an important role in maintaining tolerance to environmental allergens.
Herbal medicine and the immune system
There are many herbal medicines that have a traditional use in reducing symptoms of allergy. The popularity of these remedies persisted because they appeared to lower the body’s oversensitivity. Modern scientific research has now found that many of these herbal remedies, that have been used for thousands of years, may produce these anti-allergy effects because they have the ability to influence the balance of T helper cells in the body.
While herbal remedies might be able to promote balance in the immune system this does not mean that you should discontinue any medication that your doctor has prescribed for your allergies.