Just within the UK alone, millions of people are affected by at least one type of allergy, with simultaneous presence of multiple types being rather common occurrence. And what’s more, this number is constantly on the rise, especially among the children. But, what exactly is an allergy and who is at risk of getting affected by one?

What’s on this page?

At the beginning, it is important to make a distinction between allergy and allergic reaction. While allergy is a term denoting the predisposition to an allergic reaction, allergic reaction is a cluster of characteristic symptoms caused by an overreaction of the body to the presence of a harmless substance that is mistakenly identified by the immune system as a threat.

When this occurs, the body will begin producing immunoglobulin E (often abbreviated to IgE) antibodies which are then sent to the area where the perceived threat is located. This is why symptoms can vary depending on the nature of the trigger causing the allergic reaction.

Let’s take a closer look at the symptoms now.

What are the characteristic symptoms of an allergic reaction?

As mentioned, allergy symptoms can vary significantly, especially among reactions to different types of triggers. The most common areas of the body where the symptoms will manifest include the skin, respiratory tract, cardiovascular system and the gastrointestinal tract. Naturally, food allergies are most likely to produce symptoms related to the gastrointestinal tract, while airborne triggers will affect the respiratory system and so on.

The most common types of allergic reactions include:

  • Rhinitis
    • Inflammation of the nasal passages
    • Runny or blocked nose
    • Sneezing
    • Itching
  • Conjunctivitis
    • Inflammation of the eye
    • Redness of the eyes
    • Increased activity of tear glands resulting in watery eyes
  • Breathing difficulties
    • Inflammation of the airways
    • Coughing
    • Wheezing
    • Shortness of breath
    • Tightness of the chest
  • Urticarial (hives)
    • Red and raised rash
    • Itchy skin
    • Bumpy texture of the skin
  • Angioedema
    • Swelling under the skin
    • Occurs on the face, lips, eyes, hands and feet
    • Usually present with urticarial
    • Can lead to anaphylaxis
  • Gastric pain
    • Abdominal discomfort
    • Diarrhoea
    • Vomiting
  • Eczema
    • Dry, itchy, red skin patches

The most severe allergic reactions, regardless of their cause or exact trigger can result in anaphylactic shock which is a serious and potentially lethal complication.

When can allergies develop in an individual?

Allergies can manifest at any stage in an individual’s life, which is what can make them especially dangerous. For example, you might have been exposed to a certain substance throughout your life without any reaction, with this suddenly changing without any prior warning.

According to recent estimates, roughly 50% of all people will develop some form of an allergy before the age of 18. However, if you get diagnosed with allergy in childhood, then there is a chance that the condition might improve with age. However, the percentage of people that actually experience this improvement is rather limited, with 44% of all adults in the UK being diagnosed with allergy.

Am I at risk of developing allergies?

While anyone can develop an allergy, regardless of age, gender or general health condition, the predisposition towards allergies is hereditary in significant amount. More specifically, the studies in the genetics of allergies have shown that people with one allergic parent have roughly 33% chances of developing allergies as well, while those with both allergic parents have as much as 70% chances of being affected.

While this research managed to shed some light on the overall chances of developing allergies, it doesn’t say anything about the type of allergy one might develop. So, while the predispositions towards allergies are hereditary, the exact nature of the condition and the exact triggers are not.

What do genetic predispositions towards allergies mean?

Hereditary factor of allergies is directly tied to the increased production of IgE antibodies, a condition that medical experts call atopy. While being atopic doesn’t necessarily mean you will develop an allergy to certain triggers, it does significantly increase the risk of the immune system reacting disproportionately. In addition to genetic factors, environmental ones also play a role in increasing the chances of developing allergy. These factors include:

  • Excessive antibiotics use in childhood
  • Exposure to pet hair or dust mites
  • Exposure to tobacco smoke during childhood

What kinds of allergies exist?

Since an allergic reaction is a mistaken overreaction of the immune system to any harmless substance, one can, in theory, be allergic to any given substance out there. In practice, however, the triggers can be organised into a number of smaller groups that cover the majority of documented allergies.

Respiratory allergies

Respiratory triggers cause the characteristic reaction when inhaled. Due to this, the symptoms are mostly limited to the respiratory tract. The most common triggers from this category include:

  • Pollen
  • Mould
  • Animal dander
  • Dust mites

Contact allergies

Contact allergies are caused by allergens that come into direct contact with the skin. When this occurs, the immune system will view the trigger as an infection, causing a variety of characteristic symptoms. Most common contact allergens include:

  • Latex
  • Insect bites and stings

Food allergies

As the name implies, food allergies occur when the allergens are ingested. Once the immune system mistakenly identifies certain type of food as a threat, it will begin producing IgE antibodies in excessive amount. The most common trigger foods include:

  • Fruits
  • Eggs
  • Nuts
  • Seafood

It is also worth mentioning that medications can also be triggers of an allergic reaction, and most commonly, those are medications belonging to the following classes of pharmaceutical compounds:

  • Antibiotics
  • Anaesthetics
  • Contrast injections used during x-ray examinations

Allergy trends: Why are allergies on the rise?

As of now, there is no consensus in the medical community when it comes to the explanations of the increase in allergies prevalence. However, this rise is certainly not disputed. Still, it is important to mention that it is limited geographically – to the western countries and industrialised nations – thus lending credit to the theory that an increase in air pollution and decrease in early exposure to harmful microorganisms play a crucial role.

While air pollution is rather self-explanatory, the decline in exposure to bacteria as a cause for rise of allergies is something worth discussing. This theory stems from so-called hygiene hypothesis that states that today we are not exposed to the same amount of bacteria at an early age as we were in the past, mostly due to increased use of cleaning products and lack of contact between children and farm animal. Because of this, the hypothesis states, our bodies don’t develop as strong and robust immune system as was the case in the past, making problems with overreaction to harmless substances much more likely.