Allergy

What is an allergy?

Allergies are responses from the body and immune system against some common elements. An allergy occurs when the person comes into contact with these elements, which might include bee venom, pollen, pet dander, peanuts, and much more. A substance that causes the person to show an allergic reaction is termed as an allergen. The latter can be found in many drinks and foods.

Many people are not affected by these allergens. Generally, allergy is a response to harmless substances that are mistakenly deemed as hazardous by the patient’s body.

The most common types of allergies are:

  • Respiratory allergies
  • Food allergies
  • Skin allergies
  • Drug Allergies
  • Eye Allergies
  • Penicillin Allergy
  • Anaphylaxis allergy

How does allergy occur?

An allergy occurs when the body mistakes a harmless element as a threat. The immune system immediately reacts and causes few symptoms of allergy. It is an inappropriate immune response that happens unnaturally.

Any allergy has five stages for development:

Stage 1: The allergen contacts the biological cells through air, touch, or food.

Stage 2: The immune system calls out plasma cells and creates antibodies called immunoglobulin E as a reaction to an allergen.

Stage 3: The IgE comes inside the skin, respiratory tract, or gastrointestinal tract and does nothing.

Stage 4: When the body gets exposed to the allergen again, the IgE gets bound to the allergen and reacts, considering the allergen to be an intruder.

Stage 5: This stage occurs after 24 hours of the previous stage. The cells of the immune system move closer to the affected area and release the chemicals.

Symptoms

Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.

Symptoms

The symptoms of allergy vary according to the different types, as follows:

Skin reactions:

  • Itching
  • Rashes
  • Flaking
  • Peeling
  • Pollen and dust:
  • A runny nose
  • A cough
  • Watery and swollen eyes
  • Itchy nose and eyes
  • Blocked nose

Food reactions:

  • Swollen tongue
  • Diarrhea
  • Itchiness in the mouth
  • Rectal bleeding
  • Shortness of breath
  • Stomach cramps
  • Swelling on face
  • Tingling in the mouth
  • Vomiting

Drug reactions:

  • Itchiness
  • Wheezing
  • Possible anaphylaxis (the most harmful and severe allergic reaction)
  • Swollen face, lips, and tongue
  • Skin reactions

Hay fever, also called allergic rhinitis, can cause:

  • Sneezing
  • Itching of the nose, eyes or roof of the mouth
  • Runny, stuffy nose
  • Watery, red or swollen eyes (conjunctivitis)

A food allergy can cause:

  • Tingling in the mouth
  • Swelling of the lips, tongue, face or throat
  • Hives
  • Anaphylaxis

An insect sting allergy can cause:

  • A large area of swelling (edema) at the sting site
  • Itching or hives all over the body
  • Cough, chest tightness, wheezing or shortness of breath
  • Anaphylaxis

A drug allergy can cause:

  • Hives
  • Itchy skin
  • Rash
  • Facial swelling
  • Wheezing
  • Anaphylaxis

Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:

  • Itch
  • Redden
  • Flake or peel

Anaphylaxis

Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:

  • Loss of consciousness
  • A drop in blood pressure
  • Severe shortness of breath
  • Skin rash
  • Lightheadedness
  • A rapid, weak pulse
  • Nausea and vomiting

Causes

An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you’re exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms.

Common allergy triggers include:

  • Airborne allergens,such as pollen, animal dander, dust mites and mold
  • Certain foods,particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
  • Insect stings,such as from a bee or wasp
  • Medications,particularly penicillin or penicillin-based antibiotics
  • Latex or other substances you touch,which can cause allergic skin reactions

Risk factors

You might be more likely to develop an allergy if you:

  • Have a family history of asthma or allergies,such as hay fever, hives or eczema
  • Are a child
  • Have asthmaor another allergic condition

Complications

Having an allergy increases your risk of certain other medical problems, including:

  • If you have severe allergies, you’re at increased risk of this serious allergy-induced reaction. Foods, medications and insect stings are the most common triggers of anaphylaxis.
  • If you have an allergy, you’re more likely to have asthma — an immune system reaction that affects the airways and breathing. In many cases, asthma is triggered by exposure to an allergen in the environment (allergy-induced asthma).
  • Sinusitis and infections of the ears or lungs.Your risk of getting these conditions is higher if you have hay fever or asthma.

What are the complications of an allergy?

If an allergy is left undiagnosed and untreated, it can cause complications like:

  • Asthma
  • Infections of the lungs or ears or Sinusitis
  • Anaphylaxis

Prevention

Preventing allergic reactions depends on the type of allergy you have. General measures include the following:

  • Avoid known triggers.Even if you’re treating your allergy symptoms, try to avoid triggers. If, for instance, you’re allergic to pollen, stay inside with windows and doors closed when pollen is high. If you’re allergic to dust mites, dust and vacuum and wash bedding often.
  • Keep a diary.When trying to identify what causes or worsens your allergic symptoms, track your activities and what you eat, when symptoms occur and what seems to help. This may help you and your doctor identify triggers.
  • Wear a medical alert bracelet.If you’ve had a severe allergic reaction, a medical alert bracelet (or necklace) lets others know that you have a serious allergy in case you have a reaction and you’re unable to communicate.

Allergy-Prevalence

Worldwide, allergic rhinitis affects between 10% and 30 % of the population.1

Worldwide, sensitization (IgE antibodies) to foreign proteins in the environment is present in up to 40% of the population.1

Worldwide, adverse drug reactions may affect up to 10% of the world’s population and affect up to 20% of all hospitalized patients.1

8% have a food allergy
o    Approximately 6% aged 0-2 years have a food allergy
o    About 9% aged 3-5 years have a food allergy
o    Nearly 8% aged 6-10 years have a food allergy
o    Approximately 8% aged 11-13 years have a food allergy
o    More than 8.5% aged 14-18 years have a food allergy

38.7% of food allergic children have a history of severe reactions2

In 2012, 5.6% or 4.1 million children reported food allergies in the past 12 months.

Worldwide, sensitization rates to one or more common allergens among school children are currently approaching 40%-50%.

Roughly 13% of people 18 and over in the U.S. have sinusitis.

Worldwide, urticaria occurs with lifetime prevalence above 20%.3

Overall prevalence in Pakistan, according to this study, is 24.6 % for allergic rhinitis,24.04% for urticarial, 19.4% for bronchial asthma and 8.4% for eczema in age group of 12-55 years.4

Frequency of atopy/allergic asthma was 59(56.2%) and patients with raised total immunoglobulin E had more chance of developing allergic asthma than those having normal immunoglobulin E(p <0.05). Frequency of allergen sensitisation was the highest with house dust mite 35(33.3%), followed by paper mulberry 33(31.4%) and grass 28(26.7%) cases.5

The results were analyzed and it was found that allergic rhinitis (24.62%) and urticaria (24.04%) were the most common diseases.  

References

  1. World Health Organization. White Book on Allergy 2011-2012 Executive Summary. By Prof. Ruby Pawankar, MD, PhD, Prof. Giorgio Walkter Canonica, MD, Prof. Stephen T. Holgate, BSc, MD, DSc, FMed Sci and Prof. Richard F. Lockey, MD.
  2. Summary Health Statistics for U.S. Adults: National Health Interview Survey, 2010. By Jeannine S. Schiller, M.P.H., Jacqueline W. Lucas, M.P.H., Brian W. Ward, PhD and Jennifer A. Peregory, M.P.H., Division of Health Interview Statistics.
  3. Summary Health Statistics for U.S. Adults: National Health Interview Survey, 2012,
  4. Sabar MF, Akram M, Awan FI, Ghani MU, Shahid M, Iqbal Z, Kousar S, Idrees M. Awareness of Asthma Genetics in Pakistan: A review with some recommendations. Advancements in Life Sciences. 2018 Nov 25;6(1):1-0.
  5. Khan SW, Hamid A, Siddiqi FA, Bakhtawar M. Frequency of allergic asthma and common aeroallergens sensitization in Pakistani patients of bronchial asthma. Journal of the Pakistan Medical Association. 2018 Aug 1;68(8):1217-21.