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.
Top in this list is the first meals of a child since they play a crucial role in shaping up the gut and lung microbiota and thereby the immune system.
Maternal factors, for e.g, the presence of Provotella species in the pregnant mother’s gut might protect the child against food allergies.
Maternal diet is implicated since the composition of breastmilk is dependent on this.
Early exposure to microbial infections/ allergens that elicit an immune response and the use of antibiotics have been shown to impact allergy development and severity. For instance, a child will obviously be exposed to a very different array of substances when growing up on a farm vs an urban environment. However, early allergen exposure as an intentional desensitization strategy is not widely accepted though several studies have shown successful results.
Lifestyle in childhood (sedentary vs. active)
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.