What are allergies?

Allergies are the immune system’s response to allergens. Allergens are typically harmless, however, in some people, they can be deemed harmful by the body. The immune system is basically your body’s defence mechanism against invading and foreign substances. In the case of allergies and depending on the type of allergy and the manner in which it is encountered, some people may react with sneezing or wheezing or experience inflammation of the throat, nasal passages or digestive system as well as display a number of other possible symptoms including headaches, swelling, difficulty breathing, nausea and diarrhoea. Inflammation is, however, the primary symptom of allergies.

When the immune system feels as though it is under attack by any substance that is foreign to the body (also known as an antigen), it will create antibodies (immunoglobulins) to fight off the virus, bacteria or fungi that have the potential to cause infection or disease.

Usually, antibodies identify a certain allergen as a harmful invader and bind to it, rendering it inactive so that it can be destroyed and removed from the body. However, in the case of allergies, ‘invaders’ such as pollen, pet dander (dead skin cells present on a dog or cat’s coat) or food elicit an overreaction of the immune system and over production of a chemical histamine in response to substances that should not typically be deemed dangerous to the body when the allergen comes into contact with it. When this happens, histamine causes inflammation and constriction of smooth muscle within the body and an allergic reaction with accompanying symptoms is the result.

In most cases, the immune system will adjust to its environment. If someone comes into contact with a cat, for example, their immune system will note the change of environment and detect that the pet dander present is harmless. However, being allergic to pet dander means that the body reacts inappropriately to the allergen and responds in a way that views the allergen as a pathogen trying to attack or weaken the body.

The range of severity of allergies varies from each person and can range from minor irritation to severe anaphylaxis. Anaphylaxis can be a life-threatening condition and should be treated as an emergency where the patient will need immediate medical attention.

The majority of allergies cannot be cured, there are, however, a number of treatments to help relieve the symptoms of allergies.

Allergies are a common occurrence amongst many people and can be categorised into similar groups such as food, drug (medication), seasonal (caused by pollen, grass or mould) or animal allergies (usually caused by pet dander).

Allergies have more to them than meets the eye. The following information provides an in-depth look into what allergies are, their causes, complications, treatment and more. Should you be seeking a professional diagnosis, then consult with your doctor as this article is for informational purposes only.

What are the causes, complications and risk factors of allergies?

As stated, 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.

Risk factors

The risk of an allergy developing may be increased if the patient:

  • Has a family history of allergies or asthma – Should one have a history of family members with allergies or asthma, their risk of developing allergies is significantly higher. Common familial allergies include hives, eczema and hay fever. The hereditary factor of allergies is not a certainty. However, the theory is that should one’s parents have allergies, he or she may be more prone to 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 vital role in allergies and their development.
    • Asthma is a condition where one’s airways are 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 – This is due to the fact that children are more prone to developing allergies as a result of their immune system exposure having been more limited than that of an adult’s. Because of this, children can sometimes outgrow their 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 patient already 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), due to the fact that their body has previously created antibodies to fight these 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 reaction to allergens. The most common triggers are medications such as penicillin, food such as nuts and shellfish and insect 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 the patient 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 is when the patient has hay fever or allergic asthma as the sites of infection are already inflamed.

What are the symptoms of allergies?

Allergy symptoms

The symptoms of allergies are dependent on the substance that is involved, as the substance dictates what area of the body is affected and how this will manifest. For example, food is eaten, therefore the gut is affected.

Affected areas may include the airways, nasal passages and sinuses or the digestive system. The level of allergic reaction experienced will range from minor to severe. Severe cases of allergies can sometimes trigger a reaction that is known to be life-threatening, called anaphylaxis.

Allergy symptoms are as follows:

  • Hay Fever (allergic rhinitis), which can cause:
    • An itchy nose, itchy eyes or the roof of one’s mouth to itch
    • Sneezing
    • A blocked or runny nose
    • Red, watery or swollen eyes - this is also known as conjunctivitis (and in the case of allergies, allergic conjunctivitis)
  • Food allergies may cause:
    • The mouth to tingle
    • Swelling of the lips, tongue, throat and/or face
    • Hives (skin rash)
    • Anaphylaxis (a severe reaction to food where the patient’s throat can swell to a point where they cannot breathe)
  • Insect sting allergies may cause:
    • Oedema at the site of the sting, this is a large area of swelling which is the result of excess fluid in the tissues
    • Hives (skin rash) or itching all over the patient’s body
    • Coughing, tightness of the chest, shortness of breath or wheezing
    • Anaphylaxis
  • Drug allergies may cause:
    • Hives (skin rash)
    • The skin to itch
    • The face to swell
    • Wheezing
    • Anaphylaxis
  • Eczema, also known as atopic dermatitis, which is an allergic reaction of the skin, may result in the skin:
    • Peeling or flaking
    • Itching
    • Reddening
  • Allergic contact dermatitis occurs when the skin comes into contact with trigger substances such as latex, nickel (in jewellery), chemicals used to treat leather (especially on some watch straps), plants like poison ivy or poison oak, fragrances used in soaps, hair products and cosmetics. This can cause:
    • A raised, red rash
    • Blistering of the skin
    • A burning sensation or pain at the site of the rash
    • Itching of the skin


Pronounced an-a-fi-lak-sis.

As previously mentioned, there are some types of allergic reactions and allergies, which predominantly tend to include insect bites and foods, that can have a potentially life-threatening reaction if left untreated. This reaction is known as anaphylaxis and can result in the patient going into anaphylactic shock.

Some of the signs to take note of in this type of emergency situation are:

  • A skin rash
  • Vomiting and nausea
  • Difficulty breathing
  • A weak and rapid pulse
  • A drop in the blood pressure of the patient
  • Fainting

The symptoms of anaphylaxis are further explained in the following section:

Symptoms of anaphylaxis

Anaphylaxis refers to the rapid onset of a severe allergic reaction. This means that the symptoms appear soon after the patient has come into contact with the allergen. Anaphylaxis needs to be treated as an emergency situation as it is life-threatening.

There are a number of symptoms characteristic of this type of allergic reaction which appear between a few minutes or even hours after the allergen exposure.

If the exposure enters the body intravenously, for example, penicillin being injected into the body, the onset of symptoms will take place between five and 30 minutes after exposure. A food allergy will normally take longer. 

A study was done at the University of Manitoba in Canada that reported the most commonly affected anaphylaxis areas, listed in order, to be the:

  • Skin
  • Respiratory system
  • Digestive system
  • Cardiovascular system (heart)
  • Central nervous system

In the majority of the cases, two of the above areas will be affected simultaneously.

Skin symptoms of anaphylaxis

Flushing, itchiness and hives in various areas on the body are typical symptoms of anaphylaxis evident on the skin. Angioedema or oedema may also occur. This is when the tissue under the skin swells (it is typically drug-induced). It is also not uncommon to experience a burning sensation. In some cases, the patient’s throat and tongue may also swell.

If the skin rash develops into a bluish colour, this may be indicative of hypoxia, which is a lack of oxygen due to the patient’s throat closing.

Some patients also experience a stuffed or a runny nose. The covering of the front of the patient’s eye, as well as the eyelid, may also swell.

Respiratory symptoms of anaphylaxis

  • Wheezing as a result of the spasms of the bronchial muscles
  • Difficulty in breathing
  • A high-pitched wheezing noise when breathing, known as stridor, which is caused by the upper airways being obstructed due to swelling
  • Hoarseness
  • Coughing
  • Difficulty and pain when swallowing, this is known as odynophagia

Cardiovascular symptoms of anaphylaxis

The muscles in the artery walls can suddenly tighten temporarily as a result of the cells releasing histamine. This is known as a coronary artery spasm. This can sometimes lead to a heart attack, abnormal heart rhythm and even cardiac arrest (when the heart stops beating).

If the patient’s blood pressure drops, this can cause an accelerated heart rate, resulting in the patient feeling dizzy and lightheaded, which can lead to a loss of consciousnesses.

Gastrointestinal symptoms of anaphylaxis

  • Diarrhoea
  • Vomiting
  • Pelvic pain
  • Loss of bladder control
  • Abdominal cramps

When to see a doctor for allergic reactions

The symptoms of allergies can create a variety of complications. Should you feel as though you are experiencing any of the symptoms of allergies, then it is advised that you consult with your doctor in order to understand if your allergic reactions are minor or severe. This way you can get an accurate diagnosis and be informed of the available treatment options in order to manage your symptoms effectively.  

When to consult a doctor regarding food allergies

Food allergies can result in nausea, swelling, fatigue and vomiting, amongst other symptoms. It can sometimes take a while for someone to realise they have a mild reaction to certain food groups. However, should a person experience severe symptoms after eating something, then it is advised that they seek immediate medical attention as in some cases, if left untreated the symptoms can progress with each exposure to the certain food allergen.

When to visit a doctor regarding seasonal allergies

The symptoms of hay fever can often mimic the symptoms of a cold. This includes swollen eyes, congestion and a runny nose. The majority of these symptoms can be self-managed at home and with over-the-counter medications. However, should the symptoms persist and progress to being unmanageable, then the affected person should see a doctor.

When to see a doctor regarding severe allergies

Allergies that are severe and result in anaphylaxis can be life-threatening and require emergency attention and treatment. If a person knows they have a severe allergic reaction to something, they will often carry an EpiPen with them. When the symptoms appear, they should give themselves the shot immediately. An EpiPen is an injection that allows the airways to open (more on this under the section on medication).

How are allergies diagnosed?

There are a number of ways in which allergies can be accurately diagnosed. Firstly, the doctor will ask the patient to describe his or her symptoms and if they occurred after exposure to a certain substance in order to determine what their allergens are. After which, a physical examination will be performed.

For example, a rash on a person’s hands may denote that they have come into contact with latex gloves and therefore, they may be allergic to latex.  This type of allergy will be diagnosed as allergic contact dermatitis (ACD).

Food allergy

Food allergens

If someone has a food allergy, they may know exactly what causes the reaction, for example, nuts often elicit a serious allergic reaction that is blatantly obvious. 

If, however, this is not the case, the doctor may ask the patient to keep a list of the foods eaten (known as a food diary) and what causes a reaction. A process of elimination may also be introduced through eliminating certain foods from one’s diet in an attempt to determine what specific foods are allergens. After the elimination, certain food groups will then be introduced back into the diet to figure out what is causing the reaction.

Skin test

Allergy skin test

When allergies are suspected, a doctor is likely to also refer the patient to a specialised allergist for skin testing. In a skin test, the allergist (also sometimes performed by a doctor or nurse) pricks the skin, typically the skin on the inside of the patient’s arm, after which, the allergist will expose a small amount of proteins that are found in substances that have been identified as potential allergens to the pricked area. The reaction of the skin is documented. An allergic reaction to the allergen which the skin has been exposed to, results in the skin forming a rash, =becoming red or inflamed.

Blood test

The doctor or allergist may also conduct a blood test. This is known as a radioallergosorbent test, abbreviated as RAST. This tests the patient’s blood to determine whether there are antibodies present in response to the allergens. These are known as immunoglobin E allergens. A blood sample will be taken and sent to a laboratory for results.

How are allergies treated?

The treatments for allergies include:

  • Avoiding allergens – It is best to identify the triggers with a doctor and then avoid these allergens entirely. This is deemed the most vital step in the treatment and prevention of allergies.
  • Medications – Medications are dependent on the allergy and reaction. There are a number of medications that can assist in easing the symptoms and immune system response. Antihistamines are the most common form of medication, as well as eye drops and nasal sprays. Medications typically include:
    • Antihistamines
    • Leukotriene Modifiers
    • Cromolyn Sodium
    • Corticosteroids
    • Decongestants
  • Immunotherapy – This form of treatment is for severe allergies and consists of a number of injections given to the patient that contain a purified form of the allergen. Injections are normally administered over a few years.
    • Immunotherapy can also be given as a tablet placed under the tongue. This is known as a sublingual drug and is used as a treatment for only a few allergies such as an allergy to pollen. 
  • Emergency epinephrine – In the case of severe allergies, and allergies that are not relieved through means of other treatment, it is likely that the doctor will recommend the patient carry an emergency epinephrine shot with them.
    • An epinephrine shot (popular brands are known as EpiPen or Twinject), is an injection that contains epinephrine, which is a chemical that causes the blood vessels to narrow and opens up the airways in the patient’s lungs. The effect of this chemical reverses blood pressure that is severely low, relieves itching skin, hives, wheezing and a number of other allergy symptoms.

Alternative medicine

  • In alternative medicine circles, acupuncture is regarded as an effective means of treatment for those suffering from hay fever as it is thought to help clear up congestion associated with the allergic reaction. Medical evidence to prove this is still weak as there is much criticism over the way studies that claimed it as fact were conducted.
  • Research is still being conducted into the use of dietary supplements, probiotics, prebiotics and fish oil in order to prevent eczema and also into food allergies in pregnant women and the possibility of these being passed down to their children (hereditary allergies).

There are a number of natural treatments on the market. However, it is advised that patients consult with their doctor before attempting any alternative medication for their allergies.

What are the lifestyle and home remedies for allergies?

In some cases, the symptoms of allergies have been known to improve simply by means of home treatment. These treatments are:

  • Treatments for hay fever and congestion – These allergy symptoms can be improved through rinsing out the sinuses with a water and salt solution. This is known as saline nasal irrigation. It can be administered through a specially designed plastic bottle that can squeeze the liquid into the sinuses and flush out the mucous. Some people use a Neti pot or simply sniff up the liquid to flush out their nasal passages.
  • Treatment for mould allergy - Should a patient have a mould allergy, it is advised that they reduce the moisture in damp parts of their house through the use of dehumidifiers or ventilation fans.
  • Treatment for airborne allergy symptoms in the house – It is best that the patient reduces their exposure to pet dander or dust mites through frequently washing their linen and stuffed toys (in the case of children) with hot water, as well as regularly vacuuming using a fine filter. It is also advised that carpeting is replaced with hard flooring as carpets tend to ‘catch’ and store dust and pet dander. Having pets groomed regularly can reduce dander too.

How to prevent symptoms

There is no specific way to prevent allergies, but there are a number of ways to stop the symptoms from occurring. These include the following:

  • Avoiding triggers – This is specifically vital in the case of food allergies and they can be avoided more easily than airborne allergies such as pollen by simply avoiding trigger foods and examining food labels to check ingredients before consuming specific products. However, if a person is aware of the periods when there is increased pollen in the air, it is best that they stay indoors as far as possible.
  • Keeping a diary – Identify and record certain triggers - this will help the doctor know what the triggers are in order to treat them.
  • Wearing a medical band or bracelet – Should the patient have experienced a severe allergic reaction to a certain allergen such as penicillin in the past, these bracelets can be very helpful, and may even save one’s life as they help doctors in emergency situations know what the patient can or can’t have.

How to live with allergies

Allergies are a common occurrence and in most cases, do not lead to a life-threatening condition. Those with the risk of anaphylaxis can often learn how to deal with and manage their symptoms through the knowledge of what their triggers are and avoiding them.

Working with doctors and allergists can help a person make the right lifestyle changes and reduce major symptoms and complications to allow them to live a more enjoyable life, regardless of their allergies.

Eye drops for allergies

Disclaimer - is for informational purposes only. It is not intended to diagnose or treat any condition or illness or act as a substitute for professional medical advice.