Allergies: what is it, symptoms, treatment

An allergy is an overreaction of the immune system to certain substances called allergens. Let's explore together the different types of allergies.

Allergies: what is it?

An allergy is an immediate and excessive reaction of the immune system that occurs in the presence of allergens, or substances foreign to the body that are not harmful to health by themselves [1.1]. After the body comes into contact with an allergen, cells of the immune system release histamine, a chemical responsible for inflammation of the skin and mucous membranes, as well as associated signs and symptoms.[2.1]

It is good to pay attention and not to confuse the terms "allergy" and "intolerance": allergies only involve the immune system [3.1] and its response after exposure to an allergen.

Allergic types

The most common types of allergies can be divided into the following types:

• Food allergy
• Allergy to drug products
• Allergic Rhinitis
• Skin allergies

As described earlier, the substances that cause an allergic reaction are called allergens. These substances may get into the body of an allergic person through ingestion (eg food or medication), inhalation (eg dust or pollen), injection (eg some drugs) or direct contact (eg creams or cleansers). In recent years, the incidence of allergies has unfortunately increased significantly, due to factors such as environmental pollution and global warming.[19] The most common allergens include:

• Foods. Milk, Eggs, Fish, Crustacean shellfish, Tree nuts, Peanuts, Wheat, Soybeans, Sesame [4.1]. Most children with a food allergy outgrow their allergy during childhood. This is particularly true for allergy to cow's milk, wheat and hen’s eggs. For a few children, allergies to any of these foods can persist. [5.1];
• Medications used to treat seizures, contrast dyes containing iodine, Sulfa drugs and Penicillin. [6.1]
• Pollen from grass, weeds and trees is a common cause of hay fever (allergic rhinitis) symptoms [7.1];
• Dust mites [8.1];
• Spore and mold [9.1]
• The fur of domestic animals such as dogs and cats, parts of their skin, urine, and saliva [10.1];
• Latex, used for example to make disposable gloves [11.1];
• Cosmetic products (such as soaps, lotions, face and eye make up, fragrances, etc.) can provoke allergic reactions in some people.[12.1];
• Household chemical products (also known as chemical allergy) [13.1] [20];

Symptoms

Symptoms of an allergic reaction usually appear within a few minutes of exposure to the allergen [15.0] and can be very diverse and of varying degrees.

Frequent indications of an allergic reaction encompass [15.1]:

• Sneezing, accompanied by an itchy, runny, or congested nose (allergic rhinitis)
• Itchy, red, and watery eyes (conjunctivitis)
• Wheezing, chest constriction, difficulty breathing, and a cough
• Elevated, itchy, red rashes (hives)
• Swelling of the lips, tongue, eyes, or face
• Abdominal discomfort, nausea, vomiting, or diarrhea
• Dry, reddened, and fissured skin

In rare cases, an allergy can result in a serious allergic response known as anaphylaxis or anaphylactic shock, posing a potential threat to life. This condition impacts the entire body and generally manifests within minutes of encountering an allergen. Indications of anaphylaxis encompass any of the previously mentioned symptoms, in addition to: [15.2]

• Swelling of the throat and mouth
• Breathing difficulties
• Feeling faint or lightheaded
• Confusion
• Bluish skin or lips
• Fainting and loss of consciousness

Anaphylaxis constitutes a medical emergency necessitating prompt and immediate medical intervention.

Treatment

Allergy treatment depends on several factors, including symptoms, severity of symptoms, and the triggering substance. In the event of an allergic reaction, it is important to contact your physician who, after performing a physical examination and evaluating medical history, habits, and lifestyle, is able to treat minor cases where the cause can be clearly identified.

The attending physician may also refer the patient to an allergist and/or dermatologist (based on clinical symptoms) to make the correct diagnosis after conducting a series of examinations aimed at identifying the responsible allergen. These tests may include blood tests (to look for specific antibodies) [16.0] and allergy tests, such as skin prick tests (usually a drop of extract of various allergens is placed on the forearm [16.1].

• Prick test: after a small prick with a sterile needle, the drop is pierced into the skin and any allergic reactions are noted after a certain period of time) [16.1];
• Patch test (used in the diagnosis of contact dermatitis: a few swabs each containing a different allergen are applied to the skin and the substance is slowly released for 48 hours, after which any reactions are assessed) [16.2];
• Challenge test (This test occurs only under medical supervision) People with suspected food or drug allergies ingest (swallow) a small amount of an allergen. An allergist, a doctor who specializes in allergies, typically performs this test. If you develop anaphylaxis, the provider quickly gives an epinephrine injection to stop the reaction. [16.3]

In the case of allergies, avoiding exposure to the allergen is often the best way to avoid allergic reactions or to keep symptoms under control, although this isn't always possible. Here is some useful information broken down by condition:

• Food allergies: Carefully evaluate what you eat
• Pollen allergy: Please check the pollen calendar to understand the period when the allergen is most present in the air (generally in spring, but also in summer and fall there are plants that can trigger an allergic reaction), close windows as much as possible during the day and avoid green spaces during that period
• Allergies to dust mites: Clean the home environment to reduce the humidity in the rooms, wash curtains, sheets, pillowcases, and soft toys at high temperatures and frequently, and use pillows and quilts made of hypoallergenic materials and get rid of carpets [8.2]
• Mold allergy: Increase ventilation and air exchange in the home and enclosed environments; use dehumidifiers; wash sinks, bathtubs, showers, washable walls in the bathroom and kitchen regularly with bleach. Don’t leave wet, damp clothes sitting around. [9.2]
• Allergies to animals: Pets should be kept outdoors as much as possible and not allowed into bedrooms, bathe them regularly and clean the kennel, blankets or pillows they use, regularly wash bed linen, sofas, pillows etc.

To relieve symptoms, you can turn to medications that can be taken by mouth (tablets, capsules) or in the form of nasal sprays, eye drops, creams, gels, or ointments. Some medicines to treat allergies can be bought from a pharmacy without a prescription, but it is always advisable to consult your attending physician or pharmacist before using a new medicine, in order to avoid possible interactions and side effects. The medications most commonly used to treat allergy symptoms are:

• Antihistamines that blocks the action of histamine [17.1];
• Decongestants, which provide relief from nasal congestion [17.2];
• Steroids (corticosteroids), which help reduce inflammation [17.3].

Desensitizing therapy, also called specific immunotherapy, Immunotherapy is carefully timed and gradually increased exposure to allergens, particularly those that are difficult to avoid, such as pollens, dust mites and molds. The goal is to train the body's immune system not to react to these allergens.

Immunotherapy might be used when other treatments aren't effective or tolerated. [17.4].

People at risk of developing anaphylaxis should always carry an autoinjector containing adrenaline and know how to use it properly when needed [18.1]. After the administration of adrenaline, the person in anaphylactic shock should be immediately taken to the hospital for treatment.

Sources

1. https://www.allergy.org.au/patients/about-allergy/what-is-allergy - 1
2. https://www.webmd.com/allergies/allergy-basics - 1
3. https://www.health.harvard.edu/blog/food-allergy-intolerance-or-sensitivity-whats-the-difference-and-why-does-it-matter-2020013018736 - 1
4. https://www.fda.gov/food/buy-store-serve-safe-food/food-allergies-what-you-need-know - 1
5. https://www.anaphylaxis.org.uk/fact-sheet/outgrowing-a-food-allergy/ - 1
6. https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/drug-allergy - 1
7. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/pollen-allergies - 1
8. https://aafa.org/allergies/types-of-allergies/insect-allergy/dust-mite-allergy/ - 1 , 2
9. https://aafa.org/allergies/types-of-allergies/mold-allergy/ - 1 , 2
10. https://www.mayoclinic.org/diseases-conditions/pet-allergy/symptoms-causes/syc-20352192 - 1
11. https://acaai.org/allergies/allergic-conditions/latex-allergy/ - 1
12. https://www.fda.gov/cosmetics/cosmetic-ingredients/allergens-cosmetics - 1
13. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013423#s1 - 1
14. https://pubmed.ncbi.nlm.nih.gov/28748641/ - 1
15. https://www.nhsinform.scot/illnesses-and-conditions/immune-system/allergies#symptoms-of-allergies -0, 1 , 2
16. https://my.clevelandclinic.org/health/diagnostics/21495-allergy-testing -0, 1, 2 , 3
17. https://www.mayoclinic.org/diseases-conditions/allergies/in-depth/allergy-medications/art-20047403 - 1 , 2 , 3
18. https://www.anaphylaxis.org.uk/fact-sheet/adrenaline/ - 1
19. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9606573/#:~:text=Several%20epidemiological%20studies%20have%20stressed,and%20older%20adults%20(2).
20. https://www.webmd.com/allergies/chemical-allergies