When the immune system becomes hypersensitive to foods, pollen, drugs, bee venom, and other items, an allergic reaction ensues.
When these allergens are exposed, they might cause swelling, hives, and other symptoms.A substance that causes an allergic reaction is called an allergen. Many allergens are everyday substances that are harmless to most people. However, anything can be an allergen if the immune system has a specific type of adverse reaction to it.
One of the roles of the immune system is to destroy harmful substances in the body. If a person has an allergy to a substance, their immune system will react as though that substance is harmful and will try to destroy it.
Over 50 million people in the United States experience an allergic reaction each year. This reaction can lead to symptoms such as swelling. If swelling affects the airways, it can become life threatening.
Learn about the risk factors, symptoms, and treatments for allergies in this article.
What is an allergy?
Allergies develop when a person’s immune system overreacts to substances that are usually harmless.
The first time a person is exposed to an allergen, they do not usually experience a reaction. It often takes time for the immune system to build up a sensitivity to the substance.
In time, the immune system learns to recognize and remember the allergen. As it does so, it starts making antibodies to attack it when exposure occurs. This buildup is called sensitizationTrusted Source.
Some allergies are seasonal. For example, hay fever symptoms can peak between April and May, when the tree and grass pollen count in the air is higher. A person may experience a more severe reaction as the pollen count rises.
Symptoms
Inflammation and irritation are the results of an allergic reaction. However, the specific symptoms will vary depending on the allergen. Allergic reactions, for example, can develop in the gut, skin, sinuses, airways, eyes, or nasal passages.
The following are some allergy triggers and the symptoms they may induce.
Dust and pollen
- a blocked or congested nose
- itchy eyes and nose
- a runny nose
- swollen and watery eyes
- a cough
Food
- vomiting
- a 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
- diarrhea
Insect stings
- wheezing
- significant swelling at the site of the sting
- a sudden drop in blood pressure
- itchy skin
- shortness of breath
- restlessness
- hives, or a red and very itchy rash that spreads across the body
- dizziness
- a cough
- chest tightness
Medication
- wheezing
- swelling of the tongue, lips, and face
- a rash
- itchiness
If symptoms become severe, anaphylaxis can develop.
Anaphylaxis is the severest form of allergic reaction. It is a medical emergency and can be life threatening. Anaphylaxis can develop quickly, with symptoms appearing within minutes or hours of exposure to the allergen.
Research suggests that anaphylaxis most commonly affects the skin and respiratory system.
Some symptoms include:
- hives, flushing, and itchiness
- difficulty breathing
- wheezing
- swelling
- low blood pressure
- changes in heart rate
- dizziness and fainting
- loss of consciousness
Recognizing these symptoms can be crucial to receiving timely treatment.
Causes
When an allergic reaction occurs, allergens attach to antibodies produced by the body known as immunoglobin E (IgE). Antibodies defend the body against foreign and potentially dangerous chemicals.
When an allergen attaches to IgE, specific types of cells, notably mast cells, release substances that cause the allergic reaction.
One of these molecules is histamine. It causes the muscles in the airways and blood vessel walls to stiffen. It also urges the nose lining to create more mucus.
Risk elements
People who are under the age of 18 or who have a personal or family history of asthma or allergies may be more susceptible to allergies.
Some researchers have hypothesized that those born via cesarean delivery may be at a higher risk of allergies since they are not exposed to the mother’s microbiome during labor.
Common allergens
Potential allergens can appear almost anywhere.
In theory, a person can have an allergy to any food. Specific components — such as gluten, the protein present in wheat — can also trigger reactions.
The eight foods most likelyTrusted Source to cause allergies are:
- eggs, especially the whites
- fish
- milk
- peanuts
- tree nuts
- crustacean shellfish
- wheat
- soy
Some other common allergens include:
- pet fur, dander, skin flakes, or saliva
- mold and mildew
- medications, such as penicillin
- insect stings and bites
- cockroaches, caddisflies, midges, and moths
- plant pollens
- household chemicals
- metals, such as nickel, cobalt, chromium, and zinc
- latex
Diagnosis
The person should be ready to explain:
- any symptoms they have noticed
- when and how often they occur
- what seems to cause them
- any family history of allergies
- whether or not other household members have a similar reaction
The doctor may recommend some tests or refer the person to a specialist.
Tests
Below are some examples of allergy tests:
- Blood tests: These measure the levels of IgE antibodies to specific allergens in the immune system.
- Skin prick tests: A doctor will prick the skin with a small amount of a possible allergen. If the skin reacts and becomes itchy, red, or swollen, the person may have an allergy.
- Patch tests: To check for contact eczema, a doctor may tape a metal disc with a small amount of a suspected allergen to the person’s back. They will check for a skin reaction 48 hours later, and then again after 2 days.
Treatment
Avoiding the allergen is the best method to manage an allergy, however this is not always practical. Medical treatment can be beneficial in these situations.
Medications
Drugs will not cure an allergy, but they can help a person manage the symptoms of a reaction.
Many treatments are available over the counter. Before using a medication, however, a person should speak to a pharmacist or doctor.
Options include:
- Antihistamines: These block the action of histamine, which the immune system releases during a reaction.
- Decongestants: These can help relieve a blocked nose.
- Corticosteroids: These are available in the form of a pill, cream, nasal spray, or inhaler. They help reduce inflammation.
- Immunotherapy: This can help a person develop long-term tolerance. A person will take gradually increasing doses of the allergen, either as a tablet or an injection.
- Leukotriene receptor antagonists (antileukotrienes): These may help with some allergies if other treatments have not worked. The drugs block some of the chemicals that cause swelling.
Prevention and precautions
There is no way to prevent or cure an allergy, but it is possible to prevent a reaction or manage the symptoms if a reaction occurs.
Those at risk of an allergic reaction should:
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- Take measures to avoid exposure to known allergens.
- Carry two auto-injectors and know how to use them correctly.
- Inform friends, relatives, colleagues, and others about the allergy and how to use the auto-injector.
- Consider wearing a medical identification bracelet with details of the allergy.
- Seek allergy testing to know which substances to avoid.
