What is allergy and what is an allergic reaction?

Humans rely heavily on their immune systems to keep them healthy and to protect them from infections and microbial invasions. However, allergy is when the immune system causes immune overreactions and inflammatory responses which often result in hypersensitivity reactions. In fact, such hypersensitivity is exerted towards relatively harmless substances that the body considers as foreign allergens. For example, pollen, foods, drugs, mites, insects venom, and others all cause allergic reactions to some people.

In brief, an allergic reaction refers to how your body reacts towards the allergen. Indeed, a number of things happen to cause the allergic reaction, leading to IgE antibodies production. Thus, these antibodies purpose is to eliminate the allergen from your system, via histamine secretion that triggers allergy symptoms.

When is allergy season?

As spring begins during March and April, tree pollen emerges as the top allergen while weeds and grasses follow. Moreover, spring allergies last until autumn, but distinct allergens appear at different times.

Types of allergens:

Airborne:

• Pollen: The allergic reaction caused by pollen is hay fever or allergic rhinitis. Besides, these peak in spring, so it's better to stay indoors.
• Animal dander: A pet's saliva and sweat gland proteins, which are shed in dander are behind the allergy.
• Mold: As small as a pinhead, mold spores float in the air and cause allergies. Outdoors, molds exist in leaf piles, hay, mulch, and under mushrooms. Meanwhile, indoors molds grows in damp areas such as basements, bathrooms, and kitchens. Also, hot and humid weather promotes the growth of mold spores.
• Dust mites: It is a microscopic organism that lives in dust and in household materials like pillows, mattresses, carpets, and upholstery. Moreover, dust mites flourish in warm, humid environments.

Foods:

As soon as you eat a specific food, your body produces antibodies against it. In fact, the immune system's reaction can be severe in cases of severe food allergies.

• Eggs
• Milk or diary products in general
• Peanuts
• Tree nuts
• Soy
• Wheat
• Fish
• Shellfish

Insect venoms:

• Bee sting
• Wasp sting

Drugs:

• Penicillin
• Penicillin-based drugs

Latex:

People who have frequent contact with latex, such as rubber gloves used for surgical procedures or home cleaning, can develop a latex allergy.

• Latex proteins

Causes of allergy:

An allergic reaction can occur when your body views something as a potentially harmful invader. For instance, pollen, animal dander, mold, dust, foods, insect venom, latex, and dust are commonly known as allergic pathogens. Firstly, the first exposure to the allergen stimulates the immune system to produce antibodies that continue to watch out for it. Secondly, upon re-exposure, these antibodies release histamine and other chemicals that cause allergy symptoms.

Can allergies cause fever?

No, allergies doesn't include fever as a symptom. On the other hand, allergies can make you susceptible to bacterial and viral infections, and those can cause fevers. 

Can allergies cause sore throat?

There are times when allergies can cause a sore throat. As a matter of fact, it's the post-nasal drip behind the sore throat. 

Symptoms of allergy:

Without doubt, symptoms resides within the nose, sinuses, airways, skin and digestive system. Indeed, symptoms can be mild, moderate or severe, and they reflect each allergy. Therefore:

Hay fever or allergic rhinitis symptoms are:

• Eyes, nose and mouth roof itching
• Nose lining inflammation
• Sneezing
• Runny nose or congestion
• Conjunctivitis 

An insect sting allergy symptoms are:

• Sting site swelling
• Body itching
• Coughing
• Chest tightness
• Wheezing
• Shortness of breath
• Drop in blood pressure or dizziness
• Anaphylaxis

Food allergy symptoms are:

• Urticaria or red itchy hives
• Abdominal cramping and pain
• Diarrhea
• Lips, tongue, throat and face swelling
• Tongue sting and tingling
• Anaphylaxis

Drug allergy symptoms are:

• Urticaria or red itchy hives
• Face swelling
• Wheezing
• Anaphylaxis

Skin allergy "atopic dermatitis" symptoms are:

• Redness
• Itching
• Skin tends to peel

Latex allergy:

• Skin rash and itchiness
• Hives
• Conjunctivitis
• Wheezing

Anaphylaxis symptoms:

• Going unconscious
• Vomiting and nausea
• Swelling under the skin "Angioedema"
• Low blood pressure "Hypotension"
• Fast heart rate "Tachycardia"
• Breathing too fast "Tachypnea"

Do I have allergy or covid-19?

We often fall into this comparison when we feel sick, so these are allergies vs. covid-19 common symptoms:

Risk factors:

• Genetics and family history: In short, asthma and allergies are inherited from parents. 
• Environmental factors: These include airborne irritants.
• Geographic distribution: One is exposed to various types of pollen as well as pollen counts based on where one lives.
• Lack of early exposure to microbes: By exposing infants at an early age to diverse microorganisms and antigens, allergies, asthma, and other immune disorders may be decreased overall.

Allergy diagnosis:

• Medical history and physical diagnosis are the standard approach to diagnosing allergy. To clarify, while the first gives overall information about the patient's history with allergy, the second checks for symptoms the patient has.
• Skin test such as skin prick test, scratch test, and the intradermal test. To illustrate, the concept here is to introduce a minimal amount of an allergen to identify an allergic reaction towards it after 15-20 minutes.
• Blood test but it does not give as much information as the skin test. Certainly, it examines the amount of antibodies (IgE) produced by the immune system, where high levels of certain antibodies may indicate allergic reactions to certain allergens.
• Spirometry or a pulmonary function test can diagnose asthma.
• BAT (basophil activation test) detects markers on basophil surfaces that are reacting to drug-allergens (i.e., beta-lactams, muscle relaxants, etc.).
• Eosinophil levels can also be determined by collecting sputum or nasal smear.

How to get rid of allergies:

Unfortunately, there is no cure for allergies that can end them completely. Despite this fact, treatment exists to control allergies and inhibit the annoying symptoms resulting from allergies.

Treatment:

• It is important to avoid the allergen, but it does not end the allergic reaction completely. However, it's a necessary step to control the allergy and prevent symptoms.
• A dose of intramuscular epinephrine is recommended as the first-line therapy where an emergency shot such as EpiPen can help treat severe allergic reactions until a doctor can attend to your problem. Thus, if you have an allergy, you might be required to carry an emergency epinephrine shot with you always.
• In some cases, your allergy may be controlled by medication, such as pills, liquids, nasal sprays, or eyedrops. 
• Immunotherapy is the last resolve when both allergen avoidance and medication doesn't help. Above all, as part of this treatment, purified allergen extracts are injected over the course of several years. Besides, sublingual drugs are used to treat pollen allergies, and are another form of immunotherapy. Furthermore, they are are placed under the tongue until they dissolve.

Allergy complications:

Anaphylaxis is the most often fatal complication. In addition, the patient may suffer from hypotension, difficulty breathing or hypoxia, and/or circulatory failure. Besides, asthma is another complication which is induced by an allergen present in the environment. Finally, a hay fever or asthmatic individual is at a greater risk of developing sinusitis or infections of the ear or lungs.

References:

-CDC "COVID-19 vs. Allergies"

-Abbas M, Moussa M, Akel H. Type I Hypersensitivity Reaction. [Updated 2021 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560561/

-Mayo clinic "Allergies"

-Cleveland Clinic "Allergies"

-Featured image credits: https://www.freepik.com/vectors/pollution