Some say a sneeze and a stuffy nose come from allergies. However, a rash coming from touching or eating something can also be called an allergy. What are allergies then? What causes them? What happens inside the body during an allergic reaction?
Figure of an antibody and how they match with certain antigens.
WHO IS THE BAD GUY?
First, allergies are always the result of an external stimulant that ranges from airborne particles like pollen or animal hair, to ingested matter like cinnamon or certain medicines. The immune system considers these outside particles called allergens foreign to the body and will react to them accordingly. When the immune system first encounters an allergen, it releases antibodies, a group of Y-shaped proteins (1). The antibodies are also shaped to attach to specific types of allergens. This can be imagined like a lock and key. Each type of antibody (key) attaches to a specific allergen (lock). During an allergic response, the antibodies will attach to the incoming allergen. Then, this conglomerate will travel to the mast cells located in all body tissues. Most mast cells are found in surface tissues such as the skin, nose, and mucus membranes in the nose. Their main job is to secrete certain chemicals to flush out this allergen. These chemicals and the effects they have on the body result in the allergic reaction (2, 5, 6, 7). One of the chemicals secreted by the mast cell is histamine. Histamine constricts the airways causing difficulty in breathing. It also expands the vessels leading to fluid leakage. Another chemical released is leukotrienes. This causes the excessive secretion of mucus and thus a runny nose (2, 6).
AAAA-CHOO!
A collection of plant pollen, a common allergen, taken with an electron microscope magnified 500x.
The most common allergy most people think of is allergic rhinitis, also known as hay fever. This allergy is seasonal and often triggered by air particles like pollen, molds, dust mites, cleaning products, or pet hairs (2, 6). As mentioned above, the pollen and dust are the allergens that cause the body’s immune system to release antibodies. The release of these chemicals causes the constriction of airways, overproduction of mucus, and inflammation in the sinuses, which usually manifests as sneezing and a stuffy nose. Preventing hay fever can often be done by adding more omega-3 fats (fish or krill oil) into the diet, which reduces inflammation (5). Rubbing eucalyptus oil on the nose and temples is also a very soothing treatment because the strong smell of the eucalyptus clears the airways and thins out the mucus and stuffiness.
WHAT DID I TOUCH?
Another form of allergic reaction is contact dermatitis (6, 7, 10). This occurs when the body comes into contact with an object or chemical that the body reacts to as an allergen. These allergens can be any everyday object such as leather or nickel or ingredients in the soap or detergent or even the fabric of one’s clothes. For people who aren’t allergic to the allergen, nothing may happen when the allergen touches their skin. However, it is possible for a person to develop an allergic reaction to certain allergens over time. One such allergen is the formaldehyde. This compound is an adhesive used to hold together leather, or attach rubber to rubber or rubber to metal. It can be found in simple items like shoes, belts, or watch straps. When the immune system recognizes the allergen, it sends the antibodies to the mast cells on the skin and release large amounts of histamine. The histamine will cause the area of the skin touching the allergen to become inflamed, itchy, and display hives. At times, coming into contact with the allergen will cause the antibodies to travel to different areas on the body not touching the allergen. For example, it’s possible for a person who is allergic to formaldehyde to wear a leather watch on the wrist and develop a rash not only on that wrist, but also on the neck area. However, a skin patch test can determine the allergen. In this test, a doctor will stick multiple patches onto the patient’s back (11). Each patch is soaked with a liquid solution of a type of allergen. The patches stay on the patient’s back for five days. The doctor then looks at the patient’s back on the third and fifth day and determines which patch causes its respective skin area to react (11). Occasionally, an additional week is required to test more allergens. To treat contact dermatitis, it is best to wash the area with water, milk, or a saline solution to reduce the itchiness and inflammation. The area must be cleaned of any oil or residue from the allergen. Afterwards, a topical cream is usually added to prevent further irritation (10).
WHAT DID I EAT?
Another form of allergy is food allergy, which occurs when a person ingests a substance that they are allergic to. Normally the allergen is a protein that the body mistakenly identifies as a foreign substance due to a mutation in one of a few specific genes. This mutation causes the body to produce large amounts of the antibody that will react to that specific food. Since this is a genetic mutation, this allergy is often hereditary (12). Depending on where the immune system sends the antibody to interact with the mast cells, ingesting the allergen can have variable effects (12). One allergen is amoxicillin. This medicine may be a helpful antibiotic some people use to fight infections, but to others, it can be a detrimental allergen. To a person allergic to amoxicillin, ingesting it can cause them to break out into rashes all over his body and suffer from bloody diarrhea. The antibodies causes the mast cells in the skin and intestines to release histamine. The histamine makes the blood vessels more permeable, increases blood flow, and causes the blood to be excreted. Diagnosing food allergies can be a bit difficult. If the allergic reaction hasn’t proved to be dangerous, the doctor may prescribe a food challenge to test the allergen food. The patient would eat the types of food he’s had within the past few days and sees whether or not his body reacts. Skin tests can also be used, where an extract of a food is be injected just beneath the skin. If there is redness or swelling around the area of injection, this means the body’s antibodies are reacting to the food. For a safer test, a blood test may be administered. These tests will measure the levels of food-specific antibodies within the patient’s blood. Large amounts of a food-specific antibody could point to the possible allergen but it may not be correct (12).
Example of patch testing for contact dermatitis.
ANA-WHAT?
A more severe allergic reaction is anaphylaxis. This occurs when someone is heavily allergic to an allergen (food, medications, air particles, insects, or contact with a substance). Exposure to this allergen can cause a cascade of symptoms in various parts of the body. Some of these symptoms include a feeling of warmth, redness and itching in the mouth, light headed-ness, shortness of breath, throat tightness, anxiety, pain, cramps, vomiting, diarrhea, or even a drop in blood pressure. Without an immediate injection of epinephrine, anaphylaxis can be fatal (5).
CONCLUSION
Although there are many ways to treat the symptoms of an allergic reaction as they appear, the best way to avoid suffering from a reaction is to avoid the allergen. As mentioned before, allergies occur as the body reacts to a foreign stimulant. Therefore, to prevent and stop the reaction, avoid the allergen. In the case of leather belts or nickel belt buckles, alternative products are available such as rope belts. For medications such as amoxicillin, alternative medications that prove to be just as potent can also be taken. In general, to avoid having a severe allergic reaction, it’s best to avoid the allergen causing the problem all together.
Sources:
1) Britannica, T. E. (2014, March 12). Antibody. Retrieved from Encyclopedia Britannica: http://www.britannica.com/EBchecked/topic/27783/antibody
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3) Colored Version of Antibody. 2007. Retrieved February 18, 2015, from http://commons.wikimedia.org/wiki/File:Antibody.svg
4) Dartmouth College Electron Microscope Facility. Pollen from a variety of common plants. 2004. Retrieved February 18, 2015 from http://commons.wikimedia.org/wiki/File:Misc_pollen.jpg
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7) Immunology, A. A. (2014). Skin Allergy. Retrieved from American Academy of Allergy Asthma & Immunology: http://www.aaaai.org/conditions-and-treatments/allergies/skin-allergy.aspx
8) Jan Polák. 2011. Patch Test. Retrieved February 18, 2015 from http://en.wikipedia.org/wiki/Patch_test
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11) Seidu, L. (2014, September 24). Skin Testing for Allergies. Retrieved from WebMD: http://www.webmd.com/allergies/guide/skin-test?page=2
12) Stöppler, M. (2014, March 24). Food Allergy. Retrieved from Medicine.net: http://www.medicinenet.com/food_allergy/page2.htm