Allergies occur when the immune system responds to a foreign substance — such as pollen, bee venom and animal dander — or to a type of food that doesn’t cause an allergic reaction in most people.
Your immune system produces a substance known as an antibody. When you have allergies, your immune system makes antibodies that identify the allergen as harmful, even if they aren’t. When you come into contact with allergens, your immune system’s reaction can cause inflammation in your skin, sinuses, airways or digestive system.
The severity of the allergy varies from person to person and may range from mild irritation to anaphylaxis, which is a potentially life-threatening emergency. Although most allergies can’t be cured, treatments can help relieve your symptoms.
Depending on the substance in question, allergy symptoms can affect the airway, sinuses, nasal passages, skin and digestive system. Allergy symptoms range from mild to severe. In some severe cases, the allergy can provoke a life-threatening reaction called anaphylaxis.
Hay fever, also called allergic rhinitis, can cause:
Itching in the nose, eyes, or roof of the mouth.
Runny and stuffy nose
Tears and red or swollen eyes (conjunctivitis)
Food allergy can cause:
Tingling feeling in the mouth
Swelling of the lips, tongue, face or throat
An insect bite allergy can cause:
A large area of swelling (edema) at the site of the sting
Itching or urticaria all over the body
Coughing, chest tightness, wheezing, or shortness of breath
A drug allergy can cause:
Atopic dermatitis, an allergic skin condition, also called eczema, can cause the skin to:
Some types of allergies, including allergies to foods and insect stings, can cause a severe reaction known as anaphylaxis. Anaphylaxis — a life-threatening medical emergency — can cause you to go into shock. Anaphylaxis signs and symptoms include:
Low blood pressure
severe shortness of breath
Weak and fast pulse
Nausea and vomiting
When do you visit the doctor?
You might see your doctor if you have symptoms that you think may be due to an allergy, and over-the-counter allergy medications don’t provide enough relief. If you develop symptoms after starting a new medication, please contact the doctor who prescribed it immediately.
In the event of a severe allergic reaction (anaphylaxis), please call 911 or your local emergency number, or seek emergency medical help. If you are pregnant with an epinephrine auto-injector (EpiPen, Ovi-Q, others), give yourself a shot right away.
Even if your symptoms improve after an epinephrine injection, you should go to the emergency department to make sure your symptoms do not return when the effects of the injection wear off.
If you’ve had a severe allergic attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your doctor. Evaluating, diagnosing and managing long-term anaphylaxis is complex, so you’ll likely need to see an allergist and immunologist.
Allergies start when your immune system mistakenly perceives a normally harmless substance as a dangerous invader. The immune system then produces antibodies that remain on alert against the allergen. When you’re exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms.
Common allergens include:
Airborne allergens, such as pollen, pet dander, dust mites, and mold
Certain foods, especially peanuts, nuts, wheat, soy, fish, shellfish, eggs, and milk
Insect stings, such as bee or wasp stings
Medicines, especially penicillin or penicillin-based antibiotics
Latex or other materials you touch, which can cause allergic skin reactions
The risk of developing an allergic reaction may increase in the following cases:
Having a family history of asthma or allergies such as hay fever, urticaria or eczema
Being a patient
Having asthma or another allergic condition
Allergies also increase the risk of some other types of medical problems, including:
Anaphylaxis. If the patient suffers from severe allergic reactions, he is at a high risk of developing this serious allergic reaction. Food, medication, and insect bites are the most common triggers for anaphylaxis.
asthma. If a person has allergies, they are more likely to have asthma, an immune system reaction that affects the airways and breathing. In many cases, asthma is caused by allergens in the environment (allergic asthma).
Sinusitis, ear or lung infection. The risk of developing these conditions increases if the person has a fever or asthma.
Preventing allergic reactions depends on the type of allergy you have. General measures include:
Avoid known irritants. Even if you’re treating allergy symptoms, try to stay away from the triggers. For example, if you are allergic to pollen, stay indoors with windows and doors closed when pollen is flying a lot. If you’re allergic to dust mites, dust and vacuum the sheets, and wash them often.
Keep a blog. When trying to identify what causes or worsens allergy symptoms, keep track of what you do, what you eat, when symptoms occur, and what seems to be helpful. This may help you and your doctor identify irritants.
Wear a medical alert bracelet. If you’ve had a severe allergic reaction, a medical alert bracelet (or necklace) can let others know that you have a severe allergic reaction in case you have an allergic reaction and are unable to communicate.