An allergy is an overreaction of the immune system to a substance that is usually harmless. This substance is called an allergen. Allergens can be found in food, pollen, dust, pet dander, and other substances.
When a person with an allergy comes into contact with an allergen, their immune system produces antibodies called immunoglobulin E (IgE). These antibodies attach to mast cells, which are found in the tissues throughout the body. When an allergen binds to an IgE antibody, it triggers the mast cell to release histamine and other chemicals.
Causes of Allergies
The exact cause of allergies is unknown, but there are a number of factors that may play a role, including:
- Genetics: Allergies tend to run in families, suggesting that there is a genetic component to the condition.
- Hygiene hypothesis: The hygiene hypothesis suggests that the lack of exposure to infections in early childhood may lead to an increased risk of developing allergies.
- Environmental factors: Environmental factors, such as exposure to air pollution and tobacco smoke, may also increase the risk of developing allergies.
Types of Allergies
There are many different types of allergies, but some of the most common include:
- Food allergies: Food allergies are caused by a reaction to a specific food. The most common food allergies are to peanuts, milk, eggs, soy, wheat, tree nuts, fish, and shellfish.
- Pollen allergies: Pollen allergies are caused by a reaction to pollen from trees, grasses, and weeds. Pollen allergies are most common during the spring and fall when pollen levels are highest.
- Dust allergies: Dust allergies are caused by a reaction to dust mites, which are microscopic insects that live in dust. Dust allergies are most common in homes with high humidity and poor ventilation.
- Pet dander allergies: Pet dander allergies are caused by a reaction to dander, which is the skin flakes of animals. Pet dander allergies are most common in people who own dogs or cats.
Symptoms of Allergies
The symptoms of an allergic reaction can vary depending on the type of allergy and the severity of the reaction. Some common symptoms of an allergic reaction include:
- Runny nose
- Itchy eyes
- Difficulty breathing
Anaphylaxis is a severe allergic reaction that can be life-threatening. Symptoms of anaphylaxis include:
- Difficulty breathing
- Swelling of the throat or face
- Dizziness or fainting
- Rapid heart rate
- Low blood pressure
Diagnosis of Allergies
Allergies can be diagnosed by a doctor or allergist. There are a number of tests that can be used to diagnose allergies, including:
- Skin prick test: A skin prick test involves pricking the skin with a small amount of allergen and then observing the reaction.
- Blood test: A blood test can be used to measure the levels of IgE antibodies in the blood.
- Oral food challenge: An oral food challenge involves giving the patient small amounts of the suspected allergen to see if they have a reaction.
Treatment of Allergies
There is no cure for allergies, but there are a number of treatments that can help to relieve symptoms and prevent allergic reactions. Treatment options include:
- Avoiding the allergen: The best way to prevent an allergic reaction is to avoid the allergen. However, this can be difficult to do for some allergens, such as pollen and dust mites.
- Medications: There are a number of medications that can be used to relieve the symptoms of an allergic reaction. These medications include antihistamines, decongestants, and nasal steroids.
- Immunotherapy: Immunotherapy is a long-term treatment that can help to reduce the sensitivity to an allergen over time. Immunotherapy involves exposing the patient to small, increasing doses of the allergen until they can tolerate it.