Allergy

Hello, and welcome to today's biology lesson. Today, we are going to explore a fascinating topic that affects millions of people around the world: allergy. By the end of this lesson, you will understand what allergies are, what causes them, how they enter our bodies, the symptoms they produce, the different types of allergies, and most importantly, how you can protect yourself if you are prone to allergic reactions.

Let us begin with a bit of history. In 1906, a Viennese pediatrician named Clemens von Pirquet noticed something curious about his patients. Some of them reacted strongly to substances that were completely harmless to others — things like dust, pollen, and certain foods. He coined the term allergy, which comes from the Greek words meaning "other work." What he observed was essentially an improper activation of the immune system — the body's defense mechanism turning against harmless intruders.

So, what exactly is an allergy? An allergy, also called an allergic disease, is a condition caused by hypersensitivity of your immune system to something in the environment that usually causes no problems for most people. These conditions include hay fever, skin dermatitis, asthma, and food allergies.

The substances that trigger these reactions are called allergens. Common allergens include dust, pollen grains, spores, insect stings, certain fabrics, and various foods. When your body encounters an allergen, your immune system produces special proteins called immunoglobulins that are specific to that allergen. These proteins bind to the allergen and then attach to white blood cells in your body. This binding triggers the release of a chemical called histamine. It is this histamine that causes the familiar allergic symptoms: inflammation, skin rashes, and constriction of the small airways in your lungs called bronchioles — which leads to asthma.

Allergies are remarkably common, especially in developed countries. More than twenty percent of people experience allergic rhinitis — that is, a running nose. Over six percent have at least one food allergy. And more than twenty percent will suffer from allergic skin conditions at some point in their lives. Asthma affects between one and eighteen percent of people, depending on the country.

Interestingly, rates of allergic diseases appear to be rising, possibly due to increased fast food consumption, synthetic fabrics, and environmental pollutants.

Now, let us understand how allergens actually enter your body. There are three main entry routes.

First, through the skin. Substances like latex, certain types of clothing, and insect bites can trigger allergic reactions when they come into contact with your skin.

Second, through the mouth. A wide variety of foods can cause allergies, but ninety percent of food allergic reactions are caused by just eight items: cow's milk, soya, eggs, wheat, peanuts, fish, and shellfish. Milk-protein allergies are most common in children. Some people cannot tolerate milk from goats, sheep, or cows, and many also react to dairy products like cheese. Roughly ten percent of children with milk allergy will also react to beef, because beef contains small amounts of the same proteins found in cow's milk.

Third, through the nose. Pollen, spores, dust particles, and certain chemicals enter through your nasal passages. This can trigger coughing, sneezing, a running nose, itching, and watery eyes.

What symptoms should you watch for? When allergens are airborne, like dust or pollen, symptoms appear in areas that contact air: your eyes, nose, and lungs. General symptoms include irritation of the nose, sneezing, coughing and wheezing, red and watery eyes, increased mucus production in the lungs, and shortness of breath.

Food allergies produce different symptoms: abdominal pain, bloating, vomiting, diarrhea, itchy skin, and swelling. Food allergies rarely cause breathing problems.

Insect bites and certain medications like aspirin and the antibiotic penicillin can cause a severe systemic reaction called anaphylaxis. This is why doctors always ask if you have any allergies before giving you medication. During anaphylaxis, multiple organ systems can be affected — your digestive system, respiratory system, and circulatory system. Symptoms include widespread skin reactions, rashes, swelling, narrowing of airways, and low blood pressure. This reaction can begin suddenly or be delayed, and it can seem to improve before returning.

Let us look at some common allergic conditions in more detail.

Hay fever is usually caused by pollen and is particularly common when flowers are blooming. The lining of your nasal cavity becomes sensitive and inflamed, producing large amounts of mucus. This causes a running nose and sneezing. Your eyes may also become itchy, sore, and weepy.

Asthma is more serious. The muscles in the walls of your bronchioles contract, narrowing these small airways. This makes breathing difficult, causing wheezing. Attacks are often triggered by pollen or dust, sometimes by certain foods. Stress and worry can worsen attacks. Asthma can be treated with drugs that relax the bronchial muscles, widening the airways and making breathing easier.

Hives is an outbreak of swollen, pale red bumps on the skin that appear suddenly due to allergic reactions to medicines or foods.

Anaphylaxis, as mentioned, is a sudden severe reaction causing decreased blood pressure and shortness of breath. It requires immediate medical attention.

Allergies can also be classified by when they occur.

Seasonal allergies appear at specific times of year. In spring, pollen from blossoming flowers causes sneezing and sniffling. In summer, pollen continues to trigger reactions. In winter, pollutants like SO₂ and NO₂ — common in smog, especially in northern Indian cities — cause coughing, itchy eyes and nose, sneezing, running nose, and watery eyes.

Perennial allergies, on the other hand, occur year-round. Dust allergies fall into this category, often triggering asthma. Drug allergies, such as reactions to penicillin, causing diarrhea, nausea, and hives, can also happen at any time.

How can you protect yourself if you are prone to allergies?

First, understand that there is no permanent cure for allergies. Medications do provide relief, but the best strategy is avoidance. Learn which allergens trigger your reactions and stay away from them — especially with foods and medicines. Anti-allergy shots can help those with seasonal pollen allergies. If your allergies are severe, consult a doctor who specializes in treating allergic conditions.

Finally, let us discuss how allergies are diagnosed. Accurate diagnosis is essential for effective management. Two main methods are used: the skin prick test and the allergy blood test. Both are equally valid and recommended.

The skin prick test, also called puncture or prick testing, involves making tiny pricks in your skin using a small plastic or metal device. Sometimes allergens are injected just under the skin with a needle. Small amounts of suspended allergens — such as pollen, insect proteins, or peanut extracts — are applied to marked sites on your inner forearm or back. If you are allergic, a visible inflammatory reaction usually appears within thirty minutes, ranging from slight reddening to a full hive resembling a mosquito bite. A control drop is always included to ensure accurate results.

The allergy blood test is quick, simple, and can be done regardless of your age, skin condition, current medications, symptoms, or even if you are pregnant. Your blood sample is sent to a laboratory where multiple allergens can be detected from a single sample. This test is very safe because you are never exposed to actual allergens during the procedure. It measures the concentration of specific antibodies in your blood, helping determine what you are allergic to, predict disease development, estimate risk of severe reactions, and explain cross-reactivity between different allergens.

Let us quickly recap the key points from today's lesson.

First, an allergy is a hypersensitivity reaction of your immune system to normally harmless substances called allergens. Second, common allergens include dust, pollen, certain foods, insect stings, and medications. Third, allergens enter through three main routes: your skin, mouth, and nose. Fourth, symptoms range from mild — like sneezing and rashes — to severe, such as anaphylaxis. Fifth, allergies can be seasonal or perennial, and common conditions include hay fever, asthma, and hives. Sixth, while there is no permanent cure, avoiding known triggers and using appropriate medications can effectively manage allergies.

That brings us to the end of today's lesson on allergies. I hope you now have a clear understanding of why your body sometimes overreacts to harmless substances, and how you can take control of your health if allergies affect you or someone you know. Remember, knowledge is your first defense — stay curious, stay informed, and take good care of yourself. Until next time, goodbye and stay healthy!