All you need to know about Allergies

All that you wanted to know about allergies and didn't know whom to ask.

Allergies refer to immune hyperactivity toward certain substances that our bodies recognise as harmful. When the body identifies a particular environmental or dietary material as ‘foreign’ or a threat, it triggers a chain reaction or ‘immune response’ that attacks the concerned cells in an effort to eliminate the threat. This is what we see as allergic symptoms.

Children generally outgrow allergies with age. But some people have chronic (long-term) allergies and even those that worsen with each episode. Some are seasonal, while others are location-specific. Therefore, there is no definite timeline.

Substances that trigger allergic reactions are referred to as ‘allergens’.

The prevalence of certain allergens is dependent on environmental factors such as geographical location, season, climatic changes, and air currents, as well as human/ industrial activities in the vicinity. The best example of this is pollen since only pollen from particular plants accounts for a majority of the cases. Therefore, obviously, all the above-mentioned factors are essential for a specific plant species to thrive in a particular location and time.

Allergens can be classified into different categories based on their origin.

Some food ingredients, drugs, and daily-use products can cause allergies in vulnerable populations. So do household conditions (molds) and common insects, such as cockroaches


Trivia: Is ‘dust allergy’ really caused by dust particles? Check this post for the answer.

Interestingly, an episode of allergic symptoms can be triggered or aggravated by stress and anxiety, as well as some viral infections, as they can weaken the immune system.

Figure 1: Different types of allergens

Who is vulnerable to allergies?

These reactions and their severity are individual-specific as they are largely dependent on the genetic makeup. Thus, the tendency to develop allergies can run in the family, though the triggering substance may differ between the members.

It is possible for an allergy-free person to develop new allergies when they move places. Also, multiple allergies and interactions between allergies (with simultaneous exposure to the triggers) are common in the vulnerable population. Therefore, knowing the family history is important in allergy diagnosis.

Years of research have helped us identify a few risk/ protective factors (particularly during early childhood) that strongly influence the allergy profile or likelihood of allergy development later in life.

Do allergies start abruptly? Are there any warning signs?

An allergic reaction is comparable to a post-vaccination immune response. It may seem abrupt but it is a gradual process that is invisible to us.

The first few exposures to a potential allergen usually do not cause any visible symptoms. In fact, the body tries to develop ‘tolerance’. However, allergen exposure under certain conditions leads to a process called allergen sensitization, during which antibodies against the allergen are generated in the body. Research shows that the simultaneous exposure to specific factors called ‘adjuvants’ and the person’s immune tendency (say the family history of allergy a.k.a genetic predisposition) play a determining role in whether a person will become sensitive to a particular allergen.

Once sensitized, the body will elicit a strong response during subsequent exposures, the same way it defends against a disease after vaccination. This is why people are usually caught unawares.

In some cases, allergen load matters too. That is, a person becomes symptomatic only when exposed to an amount of the allergen beyond the tolerance threshold.

What are some common allergy symptoms?

Allergies are commonly known to occur in the respiratory tract, skin, eyes, and digestive system.

Respiratory organs are the most commonly affected, especially since the number of inhalable allergens is way higher than the other types. The symptoms may range from a simple runny nose to sinusitis, allergic rhinitis (hay fever), and nasal polyps to chronic/ long-term conditions like asthma (dry cough/shortness of breath). Sometimes, inflammatory responses can even block the airways, making breathing/ swallowing difficult and leading to life-threatening conditions. Such an acute response is referred to as ‘anaphylaxis’.

Allergy of the eyes present as watering, itching, irritation, and redness of the eyes; in extreme cases, blurred vision have also been reported.

Digestive symptoms, including nausea, abdominal cramping, vomiting, and diarrhoea, are common and are mostly caused by food allergens.

Skin allergies can be caused by both airborne and food allergens. They are of different types: contact dermatitis (local red patches at point of contact), hive (itchy red bumps over a large area), and eczema (dry itchy patches).

How are allergies diagnosed? How to differentiate them from infections?


Though most infections are accompanied by fever and pain, only a trained physician can tell them apart with certainty. Hence, it is important that we observe and communicate all symptoms and other relevant details: severity, frequency, patterns, and incidences preceding an episode that might help identify the causative agent.

Usually, it takes a few episodes to establish a definitive connection with an allergen.

Our interview with ENT specialist Dr. Swetha Chandrasekaran is a useful resource on this topic.

What are the treatment options?

  1. As a first step, doctors prescribe medicines for symptomatic relief.

  2. When a particular allergen is suspected or confirmed by tests, the best management strategy is Avoidance. For more on tangible avoidance strategies for dust-mite allergy is here.

  3. A potent treatment option for long-term and severe cases is immunotherapy. This is usually spread over months or a few years helps desensitize the immune system and has been shown to greatly benefit the quality of life in the long run.

Why is there a sudden surge in allergies across the world?

The following reasons have been attributed to the rise in allergies in recent times:

  • Hygiene hypothesis- overemphasis on sanitation and cleanliness can obstruct the natural course of immune development.

  • Climatic changes

  • Human invasion into new habitats

  • Frequent relocation of people for work or pleasure.


Disclaimer: Opinions expressed belong solely to the content provider. Miyara Health does not undertake any financial/reputational/legal/ health related/misrepresentational impact or other obligations/ liabilities that may arise from the content.

About the author

Ayshwarya Ravichandran, Ph.D.

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