An allergy occurs when an allergen elicits an abnormal immune system response to a substance (the allergen) that should not be typically be deemed harmful. The antibodies produced by the immune system in response to allergies (IgE – Immunoglobin E antibodies) then remain in the body to guard it and detect the allergen should it enter or come into contact with the body again.
This means that these antibodies are always present in the body, like security guards on the watch for another attack (even when the attack isn’t really an attack and should be viewed as a harmless event). Allergy sufferers, therefore, have elevated IgE levels in their blood. These antibodies stimulate the release of several chemicals of the immune system, the most prominent of which is histamine.
Histamine helps the body to rid itself of the aggravating allergen. So, when an allergen first comes into contact with the body, the immune system alerts the area affected, whether it is the skin, nose, lungs, gut, blood or mouth, to release histamines stored in the body’s mast cells (a type of white blood cell containing histamine). This action increases blood flow to the affected area, causes inflammation and alerts the other chemicals of the immune system to step in and help repair the affected site but also causes symptoms of an allergic reaction.
For example, if one’s nose comes into contact with pollen, histamines prompt the membranes (thin walls) of the nose to secrete mucous to rid the airways of the allergen. This results in the affected person sneezing, having a runny nose and then becoming congested. Excess mucous may also become bothersome for the throat and result in the nose and eyes itching.
Histamines work in the same way in an allergic response to food, eliciting a gut-reaction to rid the body of the food it identifies as an allergen, resulting in vomiting, diarrhoea or both. It is also possible, in more severe cases of allergic reaction, that symptoms progress and the airways of the throat narrow.
This is known as anaphylaxis, and in this case, the allergy sufferer can go into anaphylactic shock. When the body goes into anaphylactic shock, blood pressure drops and the airways narrow, ultimately affecting the patient’s ability to breathe. This is regarded as an emergency situation and medical help should be sought immediately.
Common allergy triggers
Allergy triggers that are commonly experienced are:
- Specific foods such as peanuts, tree nuts, soy, fish, shellfish, dairy, eggs and wheat.
- Airborne allergens such as animal dander, mould, dust mites and pollen.
- Hay fever, also known as Rhinitis, is commonly caused by pollen and results in inflammation of the nasal passages as well as watery and itchy eyes. It can be year-round or seasonal and is experienced by a number of people worldwide.
- Insect stings such as bee stings and wasp stings.
- Reactions to medications such as penicillin, which includes antibiotics that are penicillin-based.
- Substances that aggravate the skin when touched such as latex or silicone which result in a skin reaction.
Risk factors in the development of allergies
The risk of an allergy developing may be increased if the sufferer:
- Has a family history of allergies or asthma– Should one have a history of family members with allergies or asthma, the risk of developing allergies is significantly higher. Common familial allergies include hives, eczema and hay fever. While the hereditary factor of allergies is not an absolute certainty, the theory is that should one’s parents have allergies, then he or she may be more prone to developing them too. Food allergies have been pinpointed to a specific gene that can be passed from a parent to a child. This offers solid evidence that genes play a role in allergies and their development.
- Asthma is a condition wherein one's airways become inflamed and begin to swell and narrow – making it difficult to breathe. It is a chronic condition of the lungs. Allergic asthma is the most prevalent form of asthma and is often triggered by an allergy to pollen, dust, pet dander, things that come into contact with the skin or even food.
- Is a child– Children are more prone to developing allergies as a result of limited immune system exposure. As a result, children can sometimes outgrow allergies as they get older and their immune systems develop.
- Has asthma or another existing allergic reaction – As mentioned, asthma is a chronic lung condition resulting in inflammation and narrowing of the airways. Should a person have asthma, their risk of developing an allergy is heightened as asthma can provoke the symptoms of allergies and vice versa. In addition, having one kind of allergic reaction or condition can also make a person more susceptible to reacting adversely to other substances (allergens). This is due to the fact that the body has previously created specific antibodies to fight foreign substances and the immune system already feels threatened.
Having allergies can increase the risk of other medical issues, including:
- Asthma – As previously noted, having asthma can increase one’s risk of developing an allergy. However, the effect works both ways. If one has an allergy, they are more likely to develop asthma. In a majority of cases, asthma is triggered by exposure to an allergen in the surrounding environment. This is known as allergy-induced asthma.
- Anaphylaxis– This refers to a severe allergic reaction to an allergen. The most common triggers are medications such as penicillin, food such as nuts and shellfish, and insect stings (particularly bee stings).
- Fungal complications of the lungs or sinuses– The risk of contracting such conditions, often referred to as allergic bronchopulmonary aspergillosis or allergic fungal sinusitis, is increased when a person has a pre-existing allergy. Aspergillosis is an allergic reaction, infection or fungal growth which is caused by a fungus known as Aspergillus fungus. This fungus is normally found growing on dead leaves or decaying vegetation.
- Infections of the lungs or ears as well as sinusitis– The risk of contracting these conditions is higher when the sufferer has hay fever or allergic asthma, as the sites of infection are already inflamed.