Allergies occur when your immune system reacts to a foreign substance — such as pollen, bee venom or pet dander — or a food that doesn't cause a reaction in most people.

Your immune system produces substances known as antibodies. When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn't. When you come into contact with the allergen, your immune system's reaction can inflame your skin, sinuses, airways or digestive system.

The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis — a potentially life-threatening emergency. While most allergies can't be cured, treatments can help relieve your allergy symptoms.

Symptoms

Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.

Hay fever, also called allergic rhinitis, can cause:

• Sneezing
• Itching of the nose, eyes or roof of the mouth
• Runny, stuffy nose
• Watery, red or swollen eyes (conjunctivitis)

A food allergy can cause:

• Tingling in the mouth
• Swelling of the lips, tongue, face or throat
• Hives
• Anaphylaxis

An insect sting allergy can cause:

• A large area of swelling (edema) at the sting site
• Itching or hives all over the body
• Cough, chest tightness, wheezing or shortness of breath
• Anaphylaxis

A drug allergy can cause:

• Hives
• Itchy skin
• Rash
• Facial swelling
• Wheezing
• Anaphylaxis

Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:

• Itch
• Redden
• Flake or peel
• Anaphylaxis

Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:

• Loss of consciousness
• A drop in blood pressure
• Severe shortness of breath
• Skin rash
• Lightheadedness
• A rapid, weak pulse
• Nausea and vomiting
• When to see a doctor

You might see a doctor if you have symptoms you think are caused by an allergy, and over-the-counter allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the doctor who prescribed it right away.

For a severe allergic reaction (anaphylaxis), call 911 or your local emergency number or seek emergency medical help. If you carry an epinephrine auto-injector (Auvi-Q, EpiPen, 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 symptoms don't return when the effects of the injection wear off.

If you've had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your doctor. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor who specializes in allergies and immunology.

Original post: https://www.healthline.com/health/allergies