Allergy occurs when a person reacts to substances in the environment that are harmless to most people. These substances are known as allergens and are found in dust mites, pets, pollen, insects, ticks, moulds, foods and some medications.
Atopy is the genetic tendency to develop allergic diseases. When atopic people are exposed to allergens they can develop an immune reaction that leads to allergic inflammation. This can cause symptoms in the:
When a person who is allergic to a particular allergen comes into contact with it, an allergic reaction occurs:
Similar reactions can occur to some chemicals and food additives. However if they do not involve the immune system, they are known as adverse reactions, not allergy.
People experience different symptoms, depending on the allergen and where it enters the body. Allergic reactions can involve many parts of the body at the same time.
When allergens are breathed in, the release of histamine causes the lining of the nose to produce more mucus and become swollen and inflamed. It causes the nose to run and itch, and violent sneezing may occur. Eyes may start to water and people may get a sore throat.
Asthma can be triggered during an allergic reaction. When an allergen is breathed in, the lining of the passages in the lungs swells and makes breathing difficult.
Foods that commonly cause allergy include peanuts, seafood, dairy products and eggs. Cow’s milk allergy in infants may occur and can cause eczema, asthma, colic and stomach upset. Some people cannot digest lactose (milk sugar). Lactose intolerance causes stomach upsets, but should not be confused with allergy.
Skin problems that can be triggered by allergy include atopic dermatitis (eczema) and urticaria (hives).
Most allergic reactions are mild to moderate, and do not cause major problems. However, a small number of people may experience a severe allergic reaction called anaphylaxis, which requires immediate life saving medication. Allergens which may cause anaphylaxis include foods, insects and medications. People with a severe allergy should have an ASCIA Action Plan for Anaphylaxis.
Allergen avoidance or minimization relies on identifying the cause of the allergy and taking steps to reduce exposure to the allergen. For example, reducing dust mite in the home may help reduce symptoms in people who are allergic to mites.
Types of Allergies
An allergy occurs when your body’s immune system sees a certain substance as harmful. It reacts by causing an allergic reaction. Substances that cause allergic reactions are allergens.
There are many types of allergies. Some allergies are seasonal and others are year-round. Some allergies may be life-long.
It is important to work with your health care provider to create a plan to manage your allergy. Avoiding your allergens is the best way to prevent an allergic reaction.
True allergies to drugs (medicines) occur in only a small number of people. Most drug reactions are not allergic, but are side effects of the properties of the medicine. A diagnosis of the cause of the drug reaction is usually based only upon the patient’s history and symptoms. Sometimes skin testing for drug allergy is also done.
There are different types of allergic reactions to foods. There are differences between IgE-mediated allergies, non-IgE mediated allergies and food intolerances.
Bees, wasps, hornets, yellow jackets and fire ants are the most common stinging insects that cause an allergic reaction.
Non-stinging insects can also cause allergic reactions. The most common are cockroaches and the insect-like dust mite. Allergies to these two insects may be the most common cause of year-round allergy and asthma.
A latex allergy is an allergic reaction to natural rubber latex. Natural rubber latex gloves, balloons, condoms and other natural rubber products contain latex. An allergy to latex can be a serious health risk.
Mold and mildew are fungi. Since fungi grow in so many places, both indoors and outdoors, allergic reactions can occur year round.
Allergies to pets with fur are common. It is important to know that an allergy-free (hypoallergenic) breed of dog or cat does not exist.
Pollen is one of the most common triggers of seasonal allergies. Many people know pollen allergy as “hay fever,” but experts usually refer to it as “seasonal allergic rhinitis.”