What is an allergy?
Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.
Common allergens include pollen and certain food. Metals and other substances may also cause problems. Food, insect stings, and medications are common causes of severe reactions. Their development is due to both genetic and environmental factors. The underlying mechanism involves immunoglobulin E antibodies (IgE), part of the body’s immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine. Diagnosis is typically based on a person’s medical history. Further testing of the skin or blood may be useful in certain cases. Positive tests, however, may not mean there is a significant allergy to the substance in question.
Early exposure to potential allergens may be protective. Treatments for allergies include avoiding known allergens and the use of medications such as steroids and antihistamines. In severe reactions injectable adrenaline (epinephrine) is recommended. Allergen immunotherapy, which gradually exposes people to larger and larger amounts of allergen, is useful for some types of allergies such as hay fever and reactions to insect bites. Its use in food allergies is unclear.
An allergic reaction causes inflammation and irritation. The signs and symptoms depend on the type of allergen. Allergic reactions may occur in the gut, skin, sinuses, airways, eyes, and nasal passages.
Allergic reactions may be confused for other conditions. Hay fever, for example, creates similar irritations to the common cold but the causes are different.
Below is a range of various triggers and the symptoms they regularly cause in people who are allergic.
Dust and pollen
- blocked nose
- itchy eyes and nose
- runny nose
- swollen and watery eyes
- swollen tongue
- tingling in the mouth
- swelling of the lips, face, and throat
- stomach cramps
- shortness of breath
- rectal bleeding, mainly in children
- itchiness in the mouth
- swelling at the site of the sting
- a sudden drop in blood pressure
- itchy skin
- shortness of breath
- hives, a red and very itchy rash that spreads across the body
- chest tightness
- possible anaphylaxis
- swollen tongue, lips, and face
- skin rash
- possible anaphylaxis
Anaphylaxis is a quickly escalating, serious allergic reaction that sets in rapidly. It can be life-threatening and must be treated as a medical emergency.
This type of allergic reaction presents several different symptoms that can appear minutes or hours after exposure to the allergen. If the exposure is intravenous, onset is usually between 5 to 30 minutes. A food allergen will take longer to trigger anaphylactic reaction.
Researchers reported in The Journal of Allergy & Clinical Immunology that the most commonly affected areas in anaphylaxis are the skin and respiratory system.
Symptoms of anaphylaxis include:
- hives all over the body, flushing, and itchiness
- swollen tissues
- a burning sensation
- swelling of the tongue and throat.
- a possible blue tint to the skin from lack of oxygen
- a runny nose
- shortness of breath and wheezing
- pain when swallowing
- a drop in blood pressure that can speed up or slow down the heart rate
- abdominal cramps
- loss of bladder control
- pelvic pain similar to uterine cramps
- coronary artery spasm
- low blood pressure leading to high or low heart rate
- dizziness and fainting
Recognizing these symptoms can be crucial to receiving timely treatment.
A particular antibody called immunoglobin (IgE) causes allergic reactions. Antibodies are released to combat foreign and potentially harmful substances in the body.
IgE is released to destroy the allergen and causes the production of chemicals that trigger the allergic reaction.
One of these chemicals is called histamine. Histamine causes tightening of the muscles in the airways and the walls of blood vessels. It also instructs the lining of the nose to produce more mucus.
The following can be risk factors for developing allergies:
- a family history of asthma or allergies
- being a child
- having asthma
- not being exposed to enough sunlight
- having a different allergy
- birth by Caesarean section
The most common allergens
Potential allergens can appear almost anywhere.
Any food can theoretically cause an allergy. Specific components of food can also trigger allergic reactions, such as gluten, the protein found in wheat. The eight foods most likely to cause allergies are:
- eggs, especially egg-white
- nuts from trees
Other allergens include:
- animal materials, such as dust mite excrement, wool, fur, dander, or skin flakes, as well as Fel d 1, a protein found in cat saliva
- medications, such as penicillin, salicylates, and sulfonamides
- foods such as corn, celery, pumpkin, sesame, and beans
- insect stings, including wasp and bee sting venom, mosquito stings, and fire ants.
- insect bites from horseflies, blackflies, fleas, and kissing bugs
- cockroaches, caddis and lake flies, midges, and moths
- plant pollens from grass, trees, and weeds
- household chemicals
- metals, such as nickel, cobalt, chromium, and zinc
We endeavor to keep our content True, Accurate, Correct, Original and Up to Date.
If you believe that any information in this article is Incorrect, Incomplete, Plagiarised, violates your Copyright right or you want to propose an update, please send us an email to email@example.com indicating the proposed changes and the content URL. Provide as much information as you can and we promise to take corrective measures to the best of our abilities.
All content in this site is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor, psychiatrist or any other health care professional. We are not responsible or liable for any diagnosis, decision or self-assessment made by a user based on the content of our website.
Always consult your own doctor if you're in any way concerned about your health.