Overview

An allergy occurs when the immune system reacts to a foreign substance that enters the body. These substances are known as allergens. They include pollen, bee venom and pet dander. Allergies can also occur due to certain foods and medications that do not cause reactions in most people.

The immune system makes protective proteins called antibodies that attack invaders such as bacteria. But with allergies, the immune system makes antibodies that mark a particular allergen as harmful, even though it isn’t. Coming into contact with the allergen causes an immune system reaction that can inflame the skin, sinuses, respiratory tract or digestive system.

Allergic reactions vary from person to person. They can range from minor irritation to a life-threatening emergency called anaphylaxis. While most allergies cannot be cured, treatments can help relieve your allergy symptoms.

Symptoms

Allergy symptoms depend on which allergen is involved. The symptoms can affect the respiratory tract, sinuses and nasal passages, skin and digestive system. Allergic reactions can vary from mild to severe. Sometimes allergies can trigger a life-threatening reaction known as anaphylaxis.

hay fever, also called allergic rhinitis, can cause:

• The sneeze.
• Itching of the skin, nose, eyes or corners of the mouth.
• Running, stuffy nose.
• Fatigue, also called tiredness.
• Watery, red or swollen eyes, also called allergic conjunctivitis.

A food allergy can cause:

• Tingling in the mouth.
• Swelling of the lips, tongue, face or throat.
• Itchy bumps called hives.
• Stuffy nose, sneezing or watery, itchy eyes.
• Abdominal cramps, vomiting or diarrhoea.
• Anaphylaxis.

An insect sting allergy can cause:

• Pain and a large area of ​​swelling called edema at the injection site.
• Itching or hives all over the body.
• Skin warmth and a change in skin color, also called flushing.
• Coughing, chest tightness, wheezing or shortness of breath.
• Anaphylaxis.

A medication allergy can cause:

• Hives.
• Itchy skin or rash.
• Swelling in the face.
• Hissing.
• Shortness of breath.
• Vomiting or diarrhea.
• Feeling dizzy.
• Anaphylaxis.

atopic dermatitis, an allergic skin disorder, also called eczema, can cause the skin to:

• Itch.
• Form red or brown spots that may be harder to see on darker skin tones.
• Flake, peel or crack.

Anaphylaxis

Some types of allergies can trigger a severe reaction known as anaphylaxis. Certain foods, insect stings, and medications are among the allergens that can trigger this life-threatening emergency. Anaphylaxis can cause you to go into shock. Other symptoms include:

• Fainting.
• A drop in blood pressure.
• Severe shortness of breath and tight throat.
• Skin rash with hives or tumors.
• Dizziness.
• A fast, weak pulse.
• Stomach pain, vomiting or diarrhoea.
• A sense of doom.

When to see a doctor

You may want to see a healthcare professional if you have symptoms that you think are caused by an allergy and over-the-counter medications that were sold without a prescription didn’t give you enough relief. If you have symptoms after starting a new medication for a medical condition, call the healthcare professional who prescribed it immediately.

In the event of a severe allergic reaction, also called anaphylaxis, call 911 or your local emergency number. Or get emergency medical attention. A shot of prescription medicine called epinephrine is needed to treat anaphylaxis. If you carry an epinephrine auto-injector (Auvi-Q, EpiPen, others), give yourself a shot right away.

Even if your symptoms improve after an adrenaline shot, you should go to the emergency room. Health care professionals must make sure your symptoms do not return after the effects of the shot wear off.

If you have previously had a severe allergy attack or symptoms of anaphylaxis, you must make an appointment with your doctor. Allergy testing and creating a long-term treatment plan to manage anaphylaxis can be challenging. So you’ll likely need to see a doctor called an allergist, who diagnoses and treats allergies and other immune system conditions.

Reasons

Different substances can cause allergies. An allergy starts when the immune system mistakes a substance that is normally harmless for a dangerous invader. The immune system then forms antibodies that remain on the lookout for the specific allergen. When you are exposed to the allergen again, these antibodies can release some immune system chemicals that cause allergy symptoms.

Common allergy triggers include:

• Airborne allergens, such as pollen, animal dander, dust mites and mould.
• Certain foods, especially peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk.
• insect stings, from a bee or wasp.
• Medicines, especially penicillin or penicillin-based antibiotics.
• Latex or other substances you touch, which can cause allergic skin reactions.

Risk factors

Risk factors for allergies include:

• Having a family history of asthma or allergies, such as hayfever, hives or eczema.
• To be a child.
• Has asthma or another allergic condition.

Complications

Having an allergy increases the risk of certain other health conditions called complications, including:

• Anaphylaxis. If you have severe allergies, it increases your risk of this severe allergic reaction. Food, medicine, latex and insect stings are the most common triggers of anaphylaxis.
• Asthma. If you have an allergy, you are more likely to have asthma. Asthma is an immune system reaction that affects the airways and breathing. Asthma is often triggered by exposure to an allergen in the environment. This is known as allergy-induced asthma.
• Infections in the sinuses, ears or lungs. Your risk of getting these conditions is higher if you have hay fever or asthma.

Prevention

Prevention of allergic reactions depends on the type of allergy you have. General measures include the following:

• Stay away from known triggers. Do this even if you are receiving treatment for your allergy symptoms. For example, if you are allergic to pollen, stay indoors with windows and doors closed when pollen is high. If you are allergic to dust mites, dust and vacuum and wash bedding often. You can also use “mite proof” covers for items such as pillows, duvets, mattresses and box springs.
• Before diary. When you’re trying to figure out what’s causing your allergy symptoms or making them worse, track your activities and what you eat. Also note when symptoms occur and what seems to help. This can help you and your health care professional find your triggers.
• Wear a medical alert bracelet. If you have had a severe allergic reaction, wear a medical alert band or necklace. It lets others know that you have a severe allergy if you have a reaction and you are unable to speak.