Allergens- Types and Entry Routes: Have you suddenly started sneezing or wheezing for no reason when you go to a new place, and it stopped when you went away? Did this happen to you? This is because some of us are sensitive to certain particles like dust, pollens, etc., present in the environment. The reaction mentioned above could be because of allergies to pollen, mites, dust, etc., that are different in different places.

These allergy-causing agents are called allergens. When these allergens come in contact with skin or, if inhaled into the body, cause allergic reactions like sneezing, coughing, rashes, etc. In most cases, these reactions are not harmful, but in people with hypersensitivity, it might cause serious harm. In this article, we will learn about allergens, their types, and their entry routes.

What are Allergens?

The exaggerated response of the immune system to certain antigens existing in the atmosphere is called allergy. The objects to which such an immune response is produced are called allergens. In simple words, allergens are substances that can cause an allergic reaction in the body.

In some cases, the immune system of a person identifies allergens as foreign or dangerous substances. In response, the immune system reacts by making a type of antibody known as IgE to fight against the allergen. This action leads to an allergic reaction.

Fig: Allergens

Important Points related to Allergens and Allergy

1. Allergens are materials that can be inhaled, swallowed or come in direct contact with the skin.
2. Common allergic reactions, like hay fever, certain varieties of asthma, and food allergiesare associated with an antibody immunoglobulin E or IgE.
3. Each IgE antibody targets a specific allergen. When IgE gets in contact with its target allergen, it triggers the release of several inflammatory chemicals, including histamines, cytokines, and leukotrienes. These chemicals then cause allergy symptoms.
4. A person can be allergic to one type of allergen but not the other. 
5. Allergic reaction symptoms will vary based on the nature and amount of allergen with which a person has come in contact. It also depends on the body’s immune system response to that allergen.
6. Symptoms can extend from mild itching or runny nose to a severe allergic reaction (anaphylaxis).
   

Fig: Common Allergens

Types of Allergens

There are several types of allergens that lead to allergic reactions in one’s body. Some of the common types of allergen are mentioned in detail below:

1. Food Allergens

Fig: Food Allergens

1. A food allergy is when the immune system has a bad reaction to a certain food or something in it.
2. The immune system produces IgE antibodies that react to the food or substance in the food. 
3. The body releases histamine and other substances too. These cause asthma, itching in the throat, difficulty in breathing, stomach aches, vomiting, or diarrhoea.
4. In highly allergic people, it does not take much of the food to cause a severe reaction.
5. Most food allergies are caused by milk, eggs, wheat, soy, tree nuts, peanuts, fish, and shellfish.
6. Food protein-induced enterocolitis syndrome (FPIES) is also termed the delayed food allergy. FPIES often affects young babies. It leads to vomiting and severe fluid loss (dehydration). The most common cause of FPIES are milk, soy, or grains.
7. Symptoms may include swelling and itching of lip and mouth, tightness in the throat, hoarse voice, nausea, vomiting, diarrhoea, pains, itchy, raised bumps (hives), swelling of the skin, etc. These symptoms vary from person to person.
8. There is no medication to prevent food allergies. Hence, it is always better to avoid food that causes allergies in an individual.

2. Pollen Allergens

Fig: Pollens

1. Pollen are small, mostly yellow powder-like grains produced by trees, weeds, grasses and many flowering plants.
2. Exposure to pollen from various plants triggers hay fever and different seasonal allergies.
3. Sneezing, runny nose, nasal congestion, itchy or watery eyes are some symptoms of hay fever.
4. Staying indoors, closing windows and running air conditioning on windy days when pollen counts are high in the atmosphere are important preventive measures.
5. Each type of flowering plant has a pollen season. Some plants bloom in the fall, whereas others bloom in the fall.

3. Dust Allergens

Fig: Dust Mites

1. Dust allergens are allergic substances and mites present in the air.
2. Some examples of dust allergens include pathogens, feathers, pollens, spores, tiny insects and their waste.
3. Dust mites are microscopic organisms that are found in house dust. They cause reactions such as wheezing, dyspnea, tachypnea, asthma, etc.
4. They thrive in moist areas of the house and feed on the dead skin cells of humans and pet animals as well as bacteria, fungi or pollen.
5. Dust allergens can be prevented by covering mattresses and pillows, frequent washing of sheets and covers with hot water, etc.
6. People with hypersensitivity to dust allergies should avoid keeping stuffed toys, heavy carpets or curtains that are not easy to clean.

4. Animal Allergens

Fig: Animal Dander

1. Animal allergens are found in the skin, dander, saliva, and urine of animals.
2. Household pets like dogs, cats, hamsters, etc., are the most common cause of animal allergens.
3. Some common symptoms of animal allergens are sneezing, running nose, coughing, skin rash, itchy eyes, etc.
4. Allergy shots (immunotherapy) are used to treat animal allergies.
5. Medicines like antihistamines, bronchodilators, or nasal sprays are also used as treatment.

5. Insects Stings

Fig: Insects Stings

1. Insects that are members of the Hymenoptera family, such as honey bees, wasps, hornets, ants, etc., commonly cause allergic reactions.
2. Some of these insects have very harmful venom too.
3. The area around the sting shows redness, swelling, pain and itching.
4. Most of the time, these reactions occur only a few hours, except in some cases.
5. In certain cases, insect stings can be life-threatening to some people. Such reactions are called anaphylaxis.
6. Anaphylaxis includes severe symptoms such as itching and hives all over the body, swelling of throat and tongue, dizziness, headache, cramps, nausea and vomiting, shock, loss of consciousness and in the worst case, death.
7. The sting needs to be removed immediately after the bite to avoid more damage. It shouldn’t be squeezed as it may force the venom in the body.
8. Epinephrine is administered immediately after the sting, and allergy shots are recommended to prevent anaphylaxis in future.

6. Mould or Spore Allergens

Fig: Penicillium Spores

1. Many fungi produce spores as a method of reproduction. These spores can act as allergens for some people.
2. Moulds are a type of fungus that thrives in warm, moist areas. They produce allergens that are potentially harmful or toxic in nature.
3. These allergens may cause skin rashes and some respiratory problems.

7. Medicines

Fig: Medicines

1. Medicines or drugs such as Penicillin or Aspirin, etc., also cause allergic reactions in some people.
2. These reactions can range from mild to severe life-threatening.
3. One should always know if their body is allergic to a specific drug in order to prevent this type of allergy.
4. Antihistamines and steroids are recommended as a treatment. And for severe symptoms, epinephrine is needed.

Effects of Allergens on Different Organs

Fig: Allergic Reaction

Following are different types of allergens, diseases caused by them, their symptoms and route of entry.

Main Organ	Types of Allergen	Disease	Symptoms
Lung	Pollens, house dust, animal dander	Asthma	Wheezing, dyspnea, tachypnea
Nose and eyes	Pollen, dust	Rhinitis, Hay fever, Conjunctivitis	Running nose, itching and redness of eyes
Skin	Uncertain food drug	Eczema	Various types of lesions
Intestinal tract	Various food	Gastrointestinal allergies	Diarrhoea, vomiting
Systemic	Insect venom, drugs like penicillin, peanuts	Anaphylaxis	Shock, hypertension, wheezing

Entry Routes of Allergens

Various kinds of allergens enter the body through various routes such as:

Skin: Allergic reaction occurs when allergens such as latex or insect stings come in contact with skin. These reactions are distinguished by swelling, skin rashes, redness and inflammation. Skin allergy can last one to two days or more.

Mouth: Several types of foods are known for allergic reactions, such as milk, egg, soy, nuts, fish and, even milk protein. These allergens enter the body through the mouth only and induce inflammation in the digestive system.

Nose: Tiny particles and gaseous allergens invade the body through the nose, like pollen, spores, dust and chemicals. It is identified by wheezing, coughing, running nose, itching and watery eyes.

Fig: Entry Routes for Different Types of Allergens

Summary

Allergens are substances that can cause an allergic reaction. In some cases, the immune system identifies allergens as foreign or dangerous substances. As a result, the immune system reacts by making an IgE antibody to defend against these allergens. Such a reaction leads to allergy symptoms. Common allergens include animal proteins and dander, dust, drugs like antibiotics or applied directly to the skin. Food items like egg, peanut, milk, nuts, soy, fish, animal meat, and wheat also serve as an allergen for many people.

Other examples include fungal spores, insect and mite faeces, insect bites and stings due to their venom, natural rubber latex and pollens. Common allergy symptoms include coughing, sneezing, rashes or redness of the skin, itchy and watery eyes, etc. Severe symptoms include nausea, vomiting, loss of consciousness, shock and even death in some cases. There is no permanent cure for allergic reactions. Hence, safeguarding body substances that produce allergic reactions is the best preventive method. Allergy shots (immunotherapy), antihistamines and steroids are used as treatment and preventive measures for these allergens.

Frequently Asked Questions (FAQs) on Allergens- Types and Entry Routes

Q.1. What are allergens?
Ans: The exaggerated response of the immune system to certain antigens existing in the atmosphere is called allergy. The objects to which such an immune response is produced are called allergens.

Q.2. What are the different sources of allergens?
Ans: Pollen, animal dander, dust mites and moulds are airborne allergens. Some foods like peanuts, tree nuts, wheat, fish, shellfish, eggs and milk. Insect stings from a bee or wasp also cause allergies. Medications like penicillin or penicillin-based antibiotics are other sources of allergens.

Q.3. What is the most popular allergy?
Ans: Peanut allergies are among the most common and fatal of food allergies. It may cause anaphylaxis more often than the other allergies. For some people, even a minute amount of peanuts can cause a large reaction.

Q.4. What are the 7 types of allergies?
Ans: Types of allergies include drug allergy, food allergy, insect allergy, latex allergy, mould allergy, pet allergy and pollen allergy.

Q.5. How do you know if you have oral allergy syndrome?
Ans: Itching and tingling on the tongue or the roof of the mouth, swollen or numb lips, scratchy throat, sneezing and nasal congestion are symptoms of oral allergy. 

Learn Everything About Immune System Here

We hope this article on Allergens: Types and Entry Routes helps you in your preparation. Do drop in your queries in the comments section if you get stuck and we will get back to you at the earliest.