Summary
Allergy is a condition in which the immune system over-reacts to a particular biochemical substance that has entered the body, treating it as a threat. The same substance may not cause an allergy in another person (including members of the same family). The person may not even have had this allergy in the past, which means, it can develop at any point of time in life. Treating allergy involves boosting the immune system, correcting the immune system so that it does not over-react, and managing the symptoms. There are various types and triggers of allergy, as well as risk factors. In this article, we will learn more.
Introduction: How Immune System works….
The immune system is responsible for fighting foreign microorganisms and biochemicals, thereby upholding the health of the person.
Sometimes, even harmless substances, which do not trigger any immune-system response in another person (or even in the same person in the past), can trigger a severe over-reaction now. Such a reaction is called an allergy attack (history of such attacks constitute what is called an allergy) and the substance triggering the reaction is called an allergen. In most cases, the allergen is actually a protein molecule.
The physiology of the reaction is as follows. In normal times, or in people who do not show an allergy to this substance, the cilia which are tiny hairs present in the nose, airways, lungs and the GI-tract trap the biochemical(s) that come from outside the body and sweep them away (they are expelled when we sneeze, cough, blow the nose, and defecate).
But in some people, the body reacts to the presence of the allergen by producing Immunoglobulin antibodies (IgE). Such antibodies are produced even when a genuine threat such as a pathogen enters the body, and is part of the normal functioning of the immune system. The IgE then bind or attach themselves to the allergen molecules to prevent their spread through the body.
In response to this, the mast-cells, which are a type of white-blood-cells produce a range of biochemicals that are aimed at destroying the pathogen, or in this case – the allergen. One such chemical, or the most common among them, is histamine. In small amounts, histamine causes redness on the skin and itchy skin. Larger amounts of histamine in the body can cause nearby blood-vessels to dilate, mucous secretion to increase, and nearby areas to swell up. All these constitute an allergic reaction.
The specific antibody that is produced in reaction to this allergen stays in the body, constantly looking out for a repeat invasion of the allergen. When the next incursion of this allergen happens, the immune system by its memory, produces the same reaction again. That is, the mast-cells are again signalled to produce the same chemicals including histamine.
The allergic reaction (or allergies in general) can cause inflammation in the skin, sinuses, sense-organs, and digestive system. In extreme cases, it can cause what is called anaphylaxis, which makes breathing difficult. This will require emergency treatment, or it can be fatal.
Causes and Risk Factors
What causes one person to develop allergy against a particular substance while another person such as a family member to not do so, is not clearly understood. In fact, the same person may not have had the allergy in the past, and can develop it later in life. However, there are some risk factors.
- Heredity: The biggest risk factor. People whose parents and/or grandparents had a history of allergies, are at higher risk.
- Age: People who are less than 18 years of age are at higher risk due to weaker and more sensitive immune-systems than adults.
- Birth mode: People born through C-section (caesarean) delivery as against a normal childbirth could be at higher risk. However, research is still ongoing in this matter.
- Poor upkeep of home: Homes that are dirty, or located in dusty areas, are breeding ground for dust-mites, pathogens of various kinds, cockroaches and rates. Dust-mites can trigger allergies in some people. The saliva, urine and stools of cockroaches and rats can also trigger allergies.
- Excessive humidity: Homes that are located in humid areas, and which are not ventilated properly can develop mold or fungus on inner-surfaces of the homes. This too can trigger an allergy.
- Excessive vegetation: Living in a forested area or a location full of trees can expose a person to lot of pollen. This triggers a type of allergy called hay fever.
- Pets: Pet animals like cats, dogs, pigs, horses and some birds shed fur, feathers and dander (skin particles). All these can trigger allergies in some people. The saliva, urine and stools of these animals can also trigger allergies.
- Asthmatic: Asthma is a condition in which airways inside the lungs are chronically inflamed. Being asthmatic can make a person more sensitive to allergens and develop allergies.
Types of Allergies, Symptoms
Allergies are classified based on the type or source of the allergen.
- Food Allergy: The most common type of allergy. Some people are allergic to one or more of these foodstuffs: cow’s milk (allergy called as lactose intolerance) and milk products, eggs, sesame seeds, wheat, soyabean and soy products, shellfish and nuts like peanuts and tree-nuts (walnut, almond, etc). Symptoms include hives (reddish patches of upraised skin), generalized pruritus which is itching all over your body, localized pruritus which is itching in just one specific part of the body, swelling in the face, around the mouth, in the tongue and throat, nausea and vomiting.
- Pollen Allergy: Another equally common allergy, especially in cold, temperate countries. Also called Hay fever. Pollen are tiny particles emitted by plants, trees, grasses and weeds such as ragweed in some months of the year. But all through the year, one of these sources of pollen will be active, so one is exposed to pollen constantly. Symptoms include sneezing spells (repeated spells of multiple sneezes), itchy throat, congestion in the nose and lungs, and watery or itchy eyes.
- Pet Allergy: Fur, dander and feathers are shed regularly by household animals and birds. These trigger allergies in some residents of the home. Further, bacteria found in the saliva, urine and stools of these pets can also trigger allergies in some people. This is all the more prominent when pet owners spend a lot of time with the pet, cuddling them, and/or sharing a bed or sofa with them. Symptoms include itching nose, runny nose, congestion in the nose, sneezing spells and watery or itchy eyes.
- Dust mite allergy: Dust mites are tiny insects, not easily visible to the naked eye. They usually settle in the dry areas of the home such as pillows, bedsheets, window and door curtains, sofas, cushions, and even clothes stacked in wardrobes. The eggs, droppings and dead-bodies (they have a short lifespan) of these insects, trigger allergies in lot of people. They can even trigger asthma in healthy people. Symptoms of this allergy include runny nose, itchy throat, itchy eyes and symptoms that may be unique to each individual.
- Cockroach and Mice allergy: Homes that are maintained badly or kept unclean attract rats (mice) and cockroaches. While the stools, saliva and entire body of the cockroach are the allergens, when it comes to mice, allergens are the skin, urine and saliva. Symptoms include sneezing, wheezing, difficulty in breathing, congestion and unique symptoms that vary from person to person.
- Insect venom allergy: Venom are toxins found in the sting of insects such as bees, wasps, hornets, red ants and yellow jacket ants. When one is stung by these insects, the toxins enter the body. In most people, this may just cause an irritation or mild itching. But in some people, the allergic reaction is quite strong. Symptoms include hives or itching all over the body and not just the site of the sting, cramps in the abdomen, nausea, diarrhoea, severe headache, dizziness, and swelling of the throat or tongue. All these will require immediate medical attention. In rare cases, there is severe difficulty in breathing, called anaphylaxis, which requires emergency treatment.
- Mold allergy: Mold is one of the forms of fungi (others being mosses, lichens and mushrooms) that develop where there is water, or humidity (dampness) present over a long time. These reproduce through tiny spores that are spread through the air, water, or some insects. When these spores are inhaled by the residents of the home or commercial building, it can trigger an allergy in some people, and show strong symptoms. These include: irritation in the nose, throat or skin, congestion in the nose and sinuses, shortness of breath (dyspnoea), sneezing, dry cough, sore throat, watery and burning eyes.
- Eye Allergies: The eyes alone can show allergy symptoms while the rest of the body is just fine. Such a condition is called allergic conjunctivitis. The allergen triggering the same can come from a wide range of sources that include pollen, pet dander, mold, cigarette smoke, dust mites, contact-lens cleaning solution, some perfumes or cosmetics, and smoke or steam from cooking food. Symptoms include sensitivity to light, red eyes, itchy eyes, tearful eyes, burning sensation in the eyes, swelling of the eyelids and blurred vision.
- Latex allergy: Latex is a milky sap present in the rubber tree. This is harvested and used to produce natural rubber (as against synthetic rubber which is made from plastic). This rubber is used in gloves, balls used in playing sports or entertainment, balloons, condoms and bandages. People who work in plants that produce these products, people who wear them often (as in doctors and nurses), event management companies who use balloons for decorations, etc, are all repeatedly exposed to latex and develop an allergy. Symptoms include hives, itching nose, runny nose and difficulty in breathing.
- Medication allergy: Certain medication like chemotherapy drugs, antibiotics, insulin (rare cases), aspirin, NSAIDs like ibuprofen and drugs used in anaesthesia can trigger allergic reactions in some people. Symptoms include: hives, swelling in the mouth and throat, light-headedness, stomach cramps, nausea and difficulty in breathing.
Treatment (managing symptoms)
Some doctors believe allergies cannot be completely cured. While some believe, giving immunity shots will help overcome them. Either way, if one has allergies, he/she should consult a specialist and avoid self-medication.
Medications or therapies used to manage symptoms include:
- Antihistamines: These block the histamine action
- Decongestants: These relieve a blocked nose
- Corticosteroids: This helps reduce inflammation
- Allergen Immunotherapy: This helps the person develop long-term tolerance to the allergen
- Leukotriene receptor antagonists (antileukotrienes): These block some of the chemicals that induce swelling
NOTE: Take medications only when prescribed by your doctors, self-medication must be avoided under any circumstances.
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