What you should know about allergy?

9 min


The term allergy is a combination of 2 Greek words, ‘Allos’ meaning other and ‘ergos’ meaning action. It’s a pretty familiar term to everybody. But, have you ever wondered about the actual mechanism and an array of substances that can cause allergies in humans? Worldwide, the rise in prevalence of allergic diseases has continued to be on the rise. These are a common and increasing cause of illness, affecting somewhere between 15% and 20% of the population at some time in their lives. Therefore these are some of the most common chronic conditions worldwide.

Allergy is an abnormal condition to otherwise normal and harmless substances. These substances that cause allergy are allergens. It is an exaggerated response by the immune system of the body to protect from allergens. These reactions could be very mild to life-threatening conditions. A diffuse multi-systemic reaction is termed anaphylaxis (type 1 hypersensitivity reaction).

CLASSIFICATION OF ALLERGENS BASED ON FORM OF ALLERGY:

Allergens can be classified as,

  • Inhalant allergens
  • Ingested allergens
  • Injectants allergens
  • Contact allergens
  • Infected allergens

700 environmental allergens are identified, characterized, and purified. Some of the most common allergens include substances like food, mold, animal dander, insect stings, pollen, dust, latex, drugs or medication, etc.

FOOD ALLERGIES:

One of the most common forms of allergy is a food allergy. Above all, it is estimated to affect 4% of adults and about 4% to 6% of children and they commonly affect children and infants but they can occur at any age. Some common food substances that can cause allergy include,

  • Wheat, rye, barley (protein products referred to as gluten)- commonly found in items like pizza, beer, etc.
  • Soy
  • Egg
  • Milk
  • Peanuts
  • Tree nuts
  • Shellfish (shrimp, lobster, crabs-crustaceans)
  • Fishes (bass, flounder, trout, salmon, shark, etc.)
  • Mushroom

SYMPTOMS:

Some of the common symptoms of allergy include,

  • Allergy acquired through inhalation or skin allergens,
  • Sneezing
  • Itchy or runny nose
  • Hives
  • Rashes
  • Itchy or watery eyes
  • Feeling ill or tired
  • Flushing of skin
  • Allergy acquired through food might cause,
  • Vomiting
  • Diarrhea
  • Cramping
  • Allergy acquired sting from insects might cause,
  • Pain
  • Redness
  • Swelling

Certain serious manifestations of allergy include,

  • Asthma
  • Dermatitis
  • Conjunctivitis
  • Severe systemic anaphylaxis

Anaphylaxis, as we already saw is a serious form of allergic reaction and could have an onset anywhere in between 5 to 30 minutes of coming in contact with the allergic substance. The symptoms of anaphylaxis include,

  • Swellings in many parts of the body especially the throat
  • Wheezing
  • Passing out
  • Feeling of tightness in the chest
  • Cramping of the stomach
  • Pale appearance or redness of the face and body
  • Trouble swallowing
  • A hoarse voice
  • Rashes, hives or welts might be present, they might feel itchy
  • Vomiting
  • Diarrhea
  • Trouble breathing

MECHANISM BEHIND ALLERGIC REACTIONS:

To understand the actual mechanism we need to understand about the cells involved in the reaction. Certain cells include,

  • CD4+ T cells – play the central role in allergic inflammation
  • CD4+ T cells are mainly of 2 types,
  • T helper cells 1- produces interleukin-2, tumor necrosis factor-beta, and interferons that antagonize the allergic reaction
  • T helper cell 2- produces IL- 4 ,5 ,6 ,9 ,10 ,13 ,14 and interleukins 4 and 13 play the main roles in an allergic response.
  • Histamine one of the most important cell which causes the 5 symptoms of inflammation namely heat, pain, swelling, redness, and itchiness.

TYPES OF ALLERGY:

Allergic reactions could be of 4 types,

TYPE 1 ALLERGIC REACTION (IgE MEDIATED,IMMEDIATE, ANAPHYLACTIC):

  • One of the fastest and dangerous forms of an allergic reaction
  • Type 1 allergic reaction develops when the allergen stimulates the organism and produces immunoglobulin E.
  • Tissues or organs, affected in anaphylaxis, are ‘target tissues’ or ‘shock organs’. The lung is the principal shock organ in humans. Bronchospasm, laryngeal edema, respiratory distress, shock, and death may occur.

TYPE 2 ALLERGIC REACTION (CYTOTOXIC):

  • Develops when immunoglobulin’s G and M accompany the allergic reaction and these antibodies bind to an antigen on the cell surface and causes,
  • Phagocytosis of the cell through opsonic or immune adherence
  • Cytotoxicity by natural killer (NK) cells
  • Lysis through activation of the compliment system.
  • Examples include autoimmune anemias and hemolytic disease of the newborn (lysis of the red blood cells occur due to formation of anti erythrocyte antibodies), certain drug reactions like sedormid purpura.

TYPE 3 ALLERGIC REACTION (IMMUNE COMPLEX):

  • Characterized by deposition of antigen-antibody complexes in tissues, activation of compliment, and infiltration of polymorphonuclear leucocytes leading to tissue damage
  • 2 typical type 3 reactions include
  • Localized or Arthus reaction- relative antibody excess
  • Generalized or serum sickness- relative antigen excess

TYPE 4 ALLERGIC REACTION (DELAYED OR CELL-MEDIATED):

  • T-lymphocytes play an important role in this type of allergic reaction when they encounter a specific allergen, by secreting cytokines triggering an inflammatory reaction in the tissues.

DIAGNOSING ALLERGIC REACTIONS:

Diagnosing in case of emergencies usually happens with the patient informing about the allergic reaction and the details about the contact with the antigen.

Apart from these certain other diagnostic tests include,

  • Checking for specific IgE antibodies as part of the differential evaluation of diseases with a possible allergic component
  • Total IgE test:

Measures the total amount of IgE, in the patient’s blood.

The IgE is measured against a standard reference of the patient’s age and race and raised levels show that the patient is probably allergic.

IgE tests specific to allergen:

The doctor is sure that the patient underwent an allergic reaction after obtaining a history from the patient and therefore in such cases and further testing with one or more IgE tests can confirm or identify the allergen involved.

During the interpretation of the allergen-specific IgE testing, certain factors should be kept in mind as these might render small margins of error in diagnosing allergies.

Allergen standardization:

This is important to ascertain the quality of the allergen extracted and isolated and the diagnostic test should always use every allergen of the highest purity and the clinical specificity of the test is directly dependent on the origin of the allergen used, their purity, and their quantification.

Analytical standardization:

Used to measure the proteins and enable the measurements of nanogram quantities of specific IgE.

Calibrator treachability:

The calibrator should be traceable to WHO standard reference preparation must be used in the assays for quantification of specific IgE antibodies

TREATMENT OF ALLERGIES:

Let’s take a look at some of the emergency management of common sources of contacting an allergy,

  • Contact with allergen sometimes might provoke a very aggressive and severe form of an anaphylactic reaction (type 1 hypersensitivity reaction) therefore in such cases, the patient might already have some idea of the allergen, they can start by having,
  • Epi-pen, a device that is handy to take along in bags or kits wherever they travel (a form of intramuscular aid that is injected into the thighs). It is an auto-injectable form of adrenaline.
  • Avoid medication that might increase the risk or severity of anaphylaxis. For example, drugs that can give an anaphylactic reaction include beta-blockers and angiotensin-converting enzyme (ACE) inhibitors, commonly used as a hypertension medication. Report to your doctor about these allergies, they might prescribe an alternative group of medication to treat your condition.   
  • In case of an emergency like difficulty in breathing, edema, etc. seek medical attention immediately.

INSECT BITE (IF STUNG BY A BEE)

  • This usually does not lead to anaphylaxis, but in some allergic people it is possible
  • In the case of a bee-stung, the bees tend to leave their barbed sting in our skin and die off.
  • Flicking off the sting out of the skin as soon as possible will reduce the amount of the bee’s venom injected into our system
  • This is performed by the tip of our fingernails, car keys, edges of cards, etc.
  • Try not to press or squeeze the injured part of the skin, as it might break the sometimes intact venom sack or leads to the increased amount of venom spills into the body
  • In case of minor injury treatment with cold packs and cream does the work.
  • Itches are treated with oral-antihistamines.
  • In case of swelling or other reactions, cortisone tablets could be taken to settle down the swelling and these should be done after a consultation with a physician to examine the body’s condition, to rule out any serious reactions, and tailoring the dose according to the body’s needs.

Oral immunotherapy’ and ‘epicutaneous immunotheapy’ are two other means of treatment for allergies.

ORAL IMMUNOTHERAPY: (Food and Drug Administration approved)

Firstly, oral immunotherapy refers to a form of treatment performed under the supervision of an allergist or an immunologist. It starts by identifying the source of allergy. The patient is immunized by providing small amounts of the allergen.

For example, if a person is allergic to soy, very limited quantities of soy are given to the patient as these doses are usually non-allergic to the patient and the quantity of the allergen is increased after a few sessions.

A professional supervises while the therapy is done and there is always availability of certain emergency drugs. In this way, the patient becomes used immunized to that particular allergen, and in cases of sudden unexpected exposure to the allergen also the patient doesn’t develop any serious allergic reactions and is thus saved (Desensitization).

SIDE EFFECTS OF ORAL IMMUNOTHERAPY:

Oral immunotherapy although has certain side effects like gastrointestinal problems like vomiting, cramping, oral itching, rash, hives, swelling, etc. Anaphylaxis is also common in certain patients. A condition called eosinophilic esophagitis (EoE) is common which causes swelling of the throat, affects the airway, etc. The therapy is discontinued as this condition usually resolves on its own.

EPICUTANEOUS IMMUNOTHERAPY: (FoodDA APPROVED)

The term ‘epicutaneous’ means upon the skin. These are small dermal patches that contain a small amount of protein from allergic food materials. These dermal patches are stuck on the surface of the skin the procedure is the same as that of oral immunotherapy. Initially, very small amounts of the allergen are introduced into the body, and then slowly after reaching a threshold the allergic dose is increased. The patches are worn for a very short duration, in the beginning, later the timing and the dosage are increased and the patch is worn as long as 24 hours continually. However, this therapy does not affect our daily physical activities. Peanut patches are tested and used. Other allergens are still under trial and would soon be available for public use.

SIDE EFFECTS OF EPICUTANEOUS IMMUNOTHERAPY:

Unlike oral immunotherapy, people who took epicutaneous immunotherapy did not experience any gastrointestinal symptoms. The explanation behind this might be the route of administration used for both modes of immunotherapy. However, the participants in the trials for these dermal patches experienced mild to moderate skin reactions and a few of them had anaphylactic episodes too.

The following are performed in cases of severe reactions, after bringing the patient for definitive care to the hospital,

  • Administration of epinephrine in the ratio of 1/1000
  • Administration of histamine blockers if no cardiovascular or respiratory involvement is found. This rapidly measured to administer intravenous or intra-muscular chlorpheniramine or diphenhydramine. Administration of oral chlorpheniramine is done.
  • Monitoring the vital signs every 5 minutes is very important. In case of respiratory distress, oxygen is administered, if hypotension is found them the patient is kept in a supine position.
  • Epinephrine is repeated if cardiovascular and respiratory involvement persists.
  • Proper medical consultation from an allergy specialist or immunologist is essential.

SIMPLE TIPS ON AVOIDING ALLERGIES:

Reading and checking on food labels is one skill to master if you are a food-allergic person and checking for the date of expiry, frequent checking up on the carbs, fats, and protein levels are not enough.

  • Develop the habit of reading the labels however boring it might be. Certain ingredients are given under an umbrella term and do not mention the individual ingredients. Read after the words ‘ may contain’ (precautionary allergen labels or PAL’s), for example, it might go like ‘the product may contain milk’. Consumers can alert themselves by this design. Check for allergen information.
  • Also, be careful about improvised products. For example, the label might read ‘butter’, which we should be aware is a product of milk.

OTHER IMPORTANT POINTS TO KEEP IN MIND INCLUDE,

  • Keep in mind, to work with your doctor in knowing more about your allergy and your family member’s especially children.
  • Keep your emergency drugs handy and carry them with you. At home, it is important to locate them easily and every family member should have knowledge of their usage
  • At places like restaurants, let your waiter/bearer know what is safe for you, and ask them to check for allergens in your food
  • Never hesitate to ask your host at a guest’s home to know about your allergens present in the food served.

IN CONCLUSION,

Thus we can conclude by adding, these simple tips can go a long way from saving us and avoiding a lot of trouble. Be aware of what you eat since allergens can not only be present directly like in the food we eat but could be involved indirectly in a lot of ways like the cosmetics we use, the gloves your hairdresser or dentist might use. So know it and inform them so that they could help you in a more effective and peaceful way and As the saying goes, ‘No one knows our body better than ourselves’ hence it is important that you protect and cherish it from staying away from your demons. Let’s slay our allergens!


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Dr Kavitha M

I am an undergraduate degree holder in dentistry. I have a great interest in music and reading. I am a linguaphile. My areas of interest lie in psychology, medical imaging, diagnostics, and oncology. I am a person who focuses more on the emerging areas of forensics.

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