Understanding Allergies: Different Types of Allergies and Their Causes

Understanding Allergies

Spring is the time for sunshine, green grass, and blooming flowers. But for some people, it’s the beginning of itchy eyes, continuous sneezing, and breathing troubles.

You get a new puppy for your son, but he can’t spend much time playing with it as he ends up having a runny nose and watery eyes. 

Yes, we are talking about allergies and almost anything can trigger them. Pollens, weeds, flowers, plants, insect bites, peanuts, milk, latex, certain medications, and the list keeps going on and on.

About 40 percent of the world’s population suffers from allergies and the number is on the rise.

So what are allergies? How are allergies caused? Can allergies be prevented? Can allergies be cured? Let’s find out!

What is an Allergy?

Allergies are reactions caused by the immune system in response to substances that are not typically harmful to the body (1).

Any substance that causes an allergic reaction is called an allergen. Most commonly inhaled or consumed, these substances trigger your immune system. Common allergens that can be inhaled include dust, pollen, and pet dander. But literally, anything can trigger an allergic reaction.

The causes of allergic reactions are varied. Allergies are often caused by food or drugs taken, there may be environmental triggers or the allergy is caused by organisms such as fungus or even mosquitos.

Allergens are of three primary types:

  • Inhaled allergens 
  • Ingested allergens
  • Contact allergens

Depending upon your body’s reaction, allergies can be mild, moderate, and even severe.

What are Allergic Reactions?

what are allergies

When an allergic individual is exposed to a particular allergen, it triggers an antibody response. This happens when you touch, inhale, or swallow an allergen (2).

The antibodies produced attach themselves to the mast cells which respond by releasing histamine. This results in inflammatory symptoms such as rashes, itching, and sneezing.

Generally associated with increased immune responses to common allergens, atopy or atopic indicates a genetic tendency towards developing allergic diseases like eczema, allergic rhinitis, or asthma.

Allergic reactions may be limited to a specific body region or they may involve many parts of the body at the same time.

Types of Allergies

There are many types of allergies. Some are seasonal while others are year-round. Some can also be life-long.

British immunologists, Coombs and Gell have classified allergic reactions into four types. They are Type I, II, III, and IV. The first three allergic reactions are called ‘immediate types of allergic reactions’ as they occur within 24 hours of exposure to the allergen (3).

Type IV occurs after 24 hours of exposure and is known as delayed allergic reactions.

We have an article dedicated to this topic.

Read more: Understanding the Four Most Common Types of Allergic Reactions

Causes of Allergies

As mentioned earlier, allergy causes can be anything from airborne allergens, foods, insect stings, and medications to latex, metal, cosmetics, or even pets (4).

Allergies can be broadly classified into 5 categories based on their causes:

  1. Food allergies
  2. Environmental allergies
  3. Drug Allergies
  4. Allergies triggered by hormones
  5. Allergies trigger by organisms

We have a complete article dedicated to this topic (link given below).

Read more: Uncovering the Root Causes of Allergies: Common Triggers and Risk Factors

Development of Allergies

As mentioned before, allergic reactions can be triggered by a wide range of substances. One type of allergy causes your eyes to itch while another one causes your body to break out in hives. Some allergic reactions are localized while others cause inflammation across your body.

Some people may have a strong reaction to a small amount of an allergen, while others need a larger amount to experience a reaction. The allergic reaction may be immediate or delayed. What causes this delay? Allergens can affect the body differently, and the symptoms can vary.

To understand allergies better, you first need to know how allergies develop.

Read more: How Do Allergies Develop?

Downstream: The Long-Term Consequences of Allergies

Allergies are much more than minor discomforts such as rashes, watery eyes, or redness. Allergic reactions can have serious, long-lasting effects if left untreated. They can become more than a seasonal or periodic nuisance and can greatly affect your quality of life.

Untreated allergies can have severe reactions related to the skin, ear, nasal passage, sinuses, and digestive system. Untreated allergies can cause secondary infection and can worsen other chronic problems such as asthma, eczema, and hives on the skin.

Some of the physical complications can be:

1. Respiratory

Bronchial asthma: It is a chronic inflammatory disease in which the airways become inflamed and swollen. This results in the tightening of the muscles around the airways causing them to narrow down leading to difficulty in breathing (5).

Allergic rhinitis: Allergic rhinitis is caused because of the allergen in the air that enters your system and presents symptoms such as sneezing, nasal congestion, postnasal drip, and nasal pruritus. It is an Ig-E-mediated immune response (6).

Sinusitis: Sinusitis can be defined as the inflammation of your sinuses. These are small air pockets behind your forehead, nose, cheekbones, and the middle of the eyes. They produce mucus that protects the body from germs by trapping them in the flowing liquid. Seasonal allergies cause acute sinusitis but persistent allergies can cause chronic sinusitis (7).

Allergic bronchitis: This is a chronic, respiratory allergic reaction that is triggered by tobacco smoke, dust, or pollution. 

Pharyngitis: The inflammation of the pharynx (in the back of the throat) is known as pharyngitis. It can cause sore throat, difficulty swallowing, sneezing, runny nose, chills, fevers, and cough (8).

2. Skin

Atopic dermatitis (AD)/Eczema: It is a chronic skin condition caused by allergic reactions. It causes itching and redness that turns into a red rash. Acute atopic dermatitis produces oozing plaques of very itchy skin and chronic atopic dermatitis manifests itself as thickened, elevated plaques (9).

Hives/ Urticaria: Hives are a common skin rash that is triggered by factors such as medication, insect stings, sunlight, stress, and certain foods. In hives or urticaria, pale red bumps or welts break out on the skin all of a sudden because of the inflammation and accumulation of fluid under the skin (10).

3. Systemic

Anaphylaxis: It is a severe allergic reaction to food, medication, or venom from insect stings. In the case of anaphylaxis, the immune system overreacts and causes a full-body allergic reaction. It can cause rash, slurred speech, confusion, nausea, low pulse, and shock, also called anaphylactic shock which can be fatal (11).

Inflammation: Inflammation is your body’s process of dealing with outside invaders such as bacteria and viruses which are considered harmful. Acute inflammation usually resolves in two weeks while chronic inflammation is linked to autoimmune disorders (12).

Before You Go…

We have broken down the topic of allergies into bite-sized chunks so you can understand the content more easily. So make sure to read the rest of the topics on allergies to find the information you need to deal with your allergies effectively.

Read more:

Part 2: Symptoms of allergies

Part 3: Diagnosis of Allergies

Part 4: Treatments and care for allergies

About Tilottama Bose 48 Articles
With a Masters in Food Science and Nutrition, Tilottama has carved a niche for herself in the Health Writing Industry. She is passionate about helping her readers make informed decisions about the food they eat. She believes in the healing power of food and in food as medicine. Tilottama is an editor and writer at Fitnesshacks.org.