Allergic reactions can take various forms and have different causes. Understanding the four most prevalent types of allergic reactions is essential in comprehending their impact on your health. An allergy occurs when the body reacts adversely to specific foods or substances.

Although allergies are more common in children, they can persist throughout a person’s life. Some allergies may resolve as a child grows older, but adults can also develop allergies to substances that previously posed no problem.


Types of Allergy Reaction

There are four types of allergic reactions: Type I, II, III, and IV. Types I, II, and III are immediate reactions that happen within 24 hours of being exposed to the allergen. On the other hand, Type IV reactions, also known as delayed reactions, usually show up after 24 hours of being exposed to the allergen.

Type I (anaphylactic reactions)

Type I reactions occur when our immune system produces IgE antibodies in response to allergens like pollen, animal dander, dust mites, or certain foods. These antibodies trigger the release of histamine and other chemicals, causing inflammation and swelling.
Some examples of Type I allergic reactions include bronchial asthma, allergic rhinitis (hay fever), allergic dermatitis (skin inflammation), food allergies, allergic conjunctivitis (eye inflammation), and anaphylaxis (severe allergic shock).

Anaphylaxis is the most severe form and requires immediate medical attention as it can cause difficulty breathing, swelling, low blood pressure, bluish skin, and shock.

Type II (cytotoxic reactions)

In this type of allergic reaction, proteins called IgG and IgM antibodies play a role. These antibodies can damage cells by activating a part of our immune system called the complement system.

Type II allergic reactions can occur in specific conditions such as autoimmune hemolytic anemia (when our immune system attacks our own red blood cells), immune thrombocytopenia (destruction of platelets in the blood), and autoimmune neutropenia (reduction in a type of white blood cells called neutrophils).

Type III (immune complex reactions)

Type III allergic reactions, known as immune complex reactions, are associated with IgG and IgM antibodies. When these antibodies combine with antigens, they create immune complexes that accumulate on tissues and organs.

As the body tries to eliminate these complexes, it ends up damaging the surrounding tissue. Symptoms usually appear several hours after exposure. Examples of Type III allergic reactions include rheumatoid arthritis, lupus, serum sickness, and Arthus reaction.

Type IV (cell-mediated allergic reactions)

Type IV allergic reactions, also known as cell-mediated allergic reactions, are called “delayed” because their symptoms take at least 24 hours to appear after coming into contact with the allergen.

In some cases, it may even take 48-72 hours for symptoms to show up. Here are some examples of Type IV allergic reactions:

Tuberculin reactions: These occur in response to the tuberculin skin test used for tuberculosis screening.

Chronic asthma: This refers to long-lasting asthma symptoms triggered by certain allergens.
Contact dermatitis: It’s a skin inflammation that happens when your skin comes into direct contact with an allergen, like certain chemicals or metals.
Fungal infections: These are caused by an overgrowth of fungi in the body, often leading to localized infections.

adults doing medical assessment in London

How To Prevent Allergies

To prevent allergies, there are several steps you can take. The first is to identify your allergens, which can include common environmental triggers such as animal dander, dust mites, mold, and pollen.

It’s possible to be allergic to multiple things or have a strong allergy to a specific allergen like cat dander.

Once you’ve identified your allergens, the next step is to eliminate or control them. For instance, if you have a pet, it’s best to avoid bringing them into your bedroom and brush them outside to prevent allergens from accumulating indoors.

When selecting furniture, choosing leather over fabric can help minimize allergen buildup.

Dust Mites

To control dust mites, use allergy-proof covers for your bedding and wash your bedding weekly in hot water to remove allergens. When it comes to pollen, keep your windows closed and use an air conditioner while indoors.

While driving, keep your car windows closed to avoid exposure to pollen. Installing high-efficiency particulate air filters in your air conditioning system and using flat or panel filters for your furnace can further help filter out allergens.

Household Mold

To address household mold, create a cleaning solution with 5 percent bleach and a small amount of detergent, then apply it to mold-affected walls. When outdoors, be aware that airborne mold from vegetation can trigger allergies.

Avoid Touching Or Rubbing Your Nose

Additionally, it’s important to avoid touching or rubbing your nose, as this can worsen allergy symptoms.

Regularly washing your hands with soap and water can help remove allergens from your skin. Wearing sunglasses and a wide-brimmed hat can provide protection against pollen entering your eyes.


All in all

If you have an allergy, the first step is to identify and avoid the allergen that triggers your reaction. If that’s not possible, your doctor may recommend other treatments.

For those who reside in London, feel free to get in touch with our specialists for a full consultation. Seeking the guidance of an allergist and undergoing allergy testing can provide crucial insights into your condition.