What are the causes of allergies?
An allergy occurs when an allergen elicits an immune system response to a substance (the allergen) that should not be deemed as harmful. The antibodies produced by the immune system as a reaction 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 watch for another attack (even when the attack isn’t really an attack and should be viewed as a harmless event). The antibodies release several chemicals of the immune system, the most prominent being histamine. This causes the body to react negatively to the allergens.
Antihistamines are common over-the-counter and prescribed medications (we will discuss these more later), due to the fact that they combat the effects of histamines. Histamines, released by the body, help the body to rid itself of the allergen. This is done through inflammation, sneezing and itching amongst other defence mechanisms of the immune system. When the 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).
When histamines are released, they boost the blood flow in the area that has come into contact with the allergen.
This results in an inflammation of the area and alerts the other chemicals of the immune system to also step in and help repair the site. Histamines will then ‘dock’ at these specific areas in the body, in cells known as receptors.
For example, if one’s nose comes into contact with pollen, the histamines prompt the membranes (thin walls) of the nose to secrete mucous to rid the airways of the allergen. This results in the patient sneezing, having a runny nose and then becoming congested. This mucous will then become bothersome for the throat and can also result in the nose and eyes itching.
Histamines work in the same way for an allergic reaction to food, eliciting a gut-reaction to rid the gut of the food it identifies as an allergen, which results in vomiting, diarrhoea or both. It is also possible, in more severe cases, that the airways of the throat narrow as a reaction.
This is a severe allergic reaction known as anaphylaxis, and in this case, the patient can go into anaphylactic shock. When the body goes into anaphylactic shock, the blood pressure will drop and the airways narrow, ultimately affecting the patient’s ability to breathe. This should be seen as an emergency situation and medical help should be immediately sought.
Allergy triggers that are commonly experienced by patients are:
- Specific foods such as peanuts, tree nuts, soy, fish, shellfish, dairy, eggs and wheat.
- Allergies that are airborne such as animal dander, mould, dust mites and pollen.
- Hay fever, also known as Rhinitis, is commonly caused by pollen and results in an 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 touched such as latex or silicone which result in a skin reaction.