Common Types of Allergies
Allergies occur when the immune system reacts to a foreign substance, such as pollen, bee venom or a pet, or a food that does not cause a reaction in most people.
The immune system produces substances known as antibodies. When you are allergic to any foreign substance, your immune system starts producing antibodies that identify it as harmful, even if it is not harmful. When you come into contact with the allergen, your immune system’s reaction can infect your skin, sinuses, airways or digestive tract.
The severity of allergies varies from person to person and can range from minor complications to anaphylaxis, a potentially life-threatening emergency. While most allergies are incurable, treatments can help relieve allergy symptoms.
Allergy Symptoms
Depending on the allergen, allergy symptoms can affect the respiratory tract, sinuses and nasal passages, skin and digestive system. Allergic reactions can be mild or severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.
Hay fever, also known as allergic rhinitis, can cause the following:
- Sneezing
- Itchy nose and eyes
- Runny nose
- Inability to breathe
- Watery, red or swollen eyes (conjunctivitis)
A food allergy can cause the following:
- Tingling in the mouth
- Swelling of the lips
- Swelling of the tongue, face and throat
- Hives
- Anaphylaxis
Insect sting allergy can cause the following
- Swelling (edema) in the stung area
- Itching or hives all over the body
- Cough, chest tightness, wheezing and shortness of breath
- Anaphylaxis
A drug allergy can cause the following:
- Hives
- Itchy skin
- Swelling of the face
- Wheezing
- Anaphylaxis
The allergic skin condition atopic dermatitis, also known as eczema, causes the following skin complications:
- Itching
- Redness
- Scaly and flaking skin
- Anaphylaxis
Some types of allergies, including food and insect sting allergies, can trigger a severe reaction known as anaphylaxis. This life-threatening medical emergency can cause a person to go into shock. Symptoms of anaphylaxis include
- Loss of consciousness
- Decline in blood pressure
- Severe shortness of breath
- Skin rash
- Dizziness
- Nausea and vomiting
Allergy Causes and Common Triggers (Allergens)
An allergy starts when the immune system finds a normally harmless substance dangerous. The immune system then produces antibodies that remain alert for that allergen. When re-exposed to the allergen, these antibodies can release a range of immune system chemicals, such as histamine, which cause allergy symptoms.
Common allergy triggers include:
- Airborne allergens such as pollen, pet dander, dust mites and mold
- Certain foods, especially peanuts, nuts, wheat, soy, fish, shellfish, eggs and milk
- Bee or wasp sting
- Medicines, especially penicillin and penicillin-based antibiotics
- Latex or other chemicals that may cause allergic skin reactions
Risk factors
Having one or more of the following conditions increases the likelihood of developing allergies:
Family history of allergies such as asthma, hay fever, hives and eczema
Being a child
Having asthma or another allergic condition
Having an allergy increases the risk of serious medical problems. For example, foods, medicines and insect stings can easily send a person into shock. Also, having allergies is an invitation to asthma, and allergy-induced asthma is quite common.
People with hay fever and asthma are more likely to develop diseases such as sinusitis and ear or lung infections.
Diagnosis
If you want to find out if you have allergies, you should first see a doctor. After talking to you about your symptoms, your doctor will give you a physical examination. Then, if you think you have a food allergy, he or she will probably ask you to keep a detailed diary of the foods you eat. During the subsequent allergy assessment, he or she will ask if you have stopped eating the suspected food. Your doctor may also recommend that you have one or both of the following tests: Skin test: This test involves injecting small amounts of proteins found in potential allergens under the skin. If you are allergic, the test area on your skin will probably swell. Blood test: A specific IgE (sIgE) blood test, commonly called a radioallergosorbent test (RAST) or ImmunoCAP test, measures the amount of allergy-causing antibodies known as immunoglobulin E (IgE) antibodies in the bloodstream. The blood sample is sent to a medical laboratory.
