What is an Allergy, & When Should You See a Doctor for One?

The advent of summer brings with it vibrant blooms, but let’s be honest; things aren’t very rosy for some of us. Bloom pollen & dry weather bring with it a burden of sneezes, red eyes, itchy scalp and tickly skin. It’s fascinating how allergies can be nature’s way of reminding you, “Hey! Remember me?”

A 2020 publication by the American College of Allergy, Asthma and Immunology (ACAAI ) cogently concluded that when we look at the spectrum of allergy as a systems disease, it will allow us to define the mechanisms of allergic disorders a lot better and improve their treatment. Stay with us as we explore what an allergy is and what its causes are.

Before we understand the meaning of allergy, we must understand the built-in army that is customised to fight elements that don’t gel well with us - our immunity. Immunity, or the immune system, is a network of body cells, chemicals and fluids that attempts to fight anything foreign and unsuitable, like dust, pollen, animal hair, dairy, nuts, beer, and the list is never-ending. While the fight ensues, what you experience is an episode of allergy. 

Over a century ago, in 1906, Clemens von Pirquet (1874-1929), a Viennese paediatrician, coined the term "allergy". This young doctor changed how we think about the immune system as not just a defence mechanism but as a multilayer protection service. 

The first exposure to a foreign object triggers a change in how we react. This can lead to 2 different responses: either you develop protection from it, or you grow sensitive to it.  You’ll only get to know if you are sensitised or protected when you encounter it again. That is precisely why exposure to the chicken pox virus builds lifelong immunity, and you are protected. However, exposure to pollen sensitises you, and you react to it every time you are exposed. This sensitisation is essentially an ‘allergy’. 

Understanding how allergies develop involves step-by-step complex mechanisms. These pathways change depending on the allergen (cause of allergy) and the mode of entry (air, food, contact, exposure, etc.)

Here’s an example: You are allergic to eggs, and you end up having a delectable bite of a muffin without knowing that it contains eggs. The egg proteins (antigens) do not sit well in your stomach and thus combine with the haptens. Haptens are carrier molecules for these foreign proteins that are about to target the immune system. The hapten-bound egg proteins bind to immune system cells to form antibodies (your future defence cells). This reaction releases chemicals (like histamine) that give you a stomach ache, rashes, etc.—an allergic reaction.

There are different immune responses, each with a specific type of allergic response. 

We know about many usual causes of allergies. Some of these are foods like peanuts, tree nuts, milk, eggs, soy, wheat, fish, and shellfish. Materials like latex and air-borne factors like pollen, dust mites, dander from furry pets, mould spores, insect bites, etc. 

There are many unusual causes of allergies that may shock you:

• The Cold: Cold urticaria is a rare condition. When exposed to sub-optimal temperatures and freezing winds, some develop hives and itching. In severe cases.
• Vibration: Odd, but yes. Vibratory urticaria is quite a rare form of physical urticaria where exposure to vibrations, such as in power tools or riding in vehicles, can cause hives, itching, and other allergic symptoms.
• Stress: Not a direct allergen; stress can exacerbate allergic reactions in some. It kicks off the release of histamine and other chemicals in the body. You have unexpected sensitivity to the skin, the eyes, and gut issues like bloating and so on. 
• Fragrances: Perfumes, colognes, and scented products may not always strike the right cord. These chemicals may trigger allergic reactions in some people, leading to skin irritation, headaches, and sneezing.
• Preservatives: Certain preservatives commonly found in foods and personal care products, such as sulphides, initiate skin issues like hives, asthma or bad tummy for the sensitive bunch.

Yes, there is an emergency aspect of allergies called anaphylaxis. Humongous amounts of histamine are released in anaphylaxis, which initiates breathing issues. This demands immediate hospital care and medicines.

Anaphylaxis is an emergency allergic reaction. It must be identified clinically by examining the symptoms, as quick allergy testing is usually unavailable. Medications administered during the first-line treatment of anaphylaxis help with the speedy reversal of allergic symptoms by restricting blood flow, relaxing the muscles of your breathing pipes, and supporting blood pressure and breathing. 

You can develop allergies at any time in your life. Keeping track of specific unusual reactions to certain foods or changes in seasons is a good place to start. When you visit your doctor, they may suggest a series of tests to see if you have any allergies and help you with a treatment plan that might involve medications and lifestyle changes to keep the allergy in check.

Medically reviewed by:

Dr Mehul S Thakkar, Respiratory Medicine