Types of Allergies
An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular 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 allergies include:
Airborne allergens, such as pollen, animal dander, dust mites and mold
Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
Insect stings, such as from a bee or wasp
Medications, particularly penicillin or penicillin-based antibiotics
Latex or other substances you touch, which can cause allergic skin reactions
You might be more likely to develop an allergy if you:
Have a family history of asthma or allergies, such as hay fever, hives or eczema
Are a child
Have asthma or another allergic condition
Having an allergy increases your risk of certain other medical problems, including:
Anaphylaxis. If you have severe allergies, you're at increased risk of this serious allergy-induced reaction. Foods, medications and insect stings are the most common triggers of anaphylaxis.
Asthma. If you have an allergy, you're more likely to have asthma — an immune system reaction that affects the airways and breathing. In many cases, asthma is triggered by exposure to an allergen in the environment (allergy-induced asthma).
Sinusitis and infections of the ears or lungs. Your risk of getting these conditions is higher if you have hay fever or asthma.