An allergy is a reaction by your immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. Substances that often cause reactions are
- Pollen (grass, weed or tree)
- Dust mites
- Mold spores
- Pet dander (cats and other furry or hairy animals such as dogs, horses, rabbits and guinea pigs)
- Foods such as peanuts, cow's milk, soy, seafood and eggs
- Insect stings and tick bites
Normally, your immune system fights germs. It is your body's defense system. In most allergic reactions, however, it is responding to a false alarm. Genes and the environment probably both play a role.
Allergies can cause a variety of symptoms such as a runny nose, sneezing, itching, rashes, swelling, or asthma. Allergies can range from minor to severe. Anaphylaxis is a severe reaction that can be life-threatening. Doctors use skin and blood tests to diagnose allergies. Treatments include medicines, allergy shots, and avoiding the substances that cause the reactions.
Which areas of the body may be affected?
Depending on the allergen and where it enters your body, you may experience different symptoms. For example, pollen, when breathed in through the nose, usually causes symptoms in the nose, eyes, sinuses and throat (allergic rhinitis). Allergy to foods usually causes stomach or bowel problems, and may cause hives (urticaria). Allergic reactions can also involve several parts of the body at the same time.
The nose, eyes, sinuses and throat
When allergens are breathed in, the release of histamine causes the lining of your nose to produce lots of mucus and to become swollen and inflamed. It causes your nose to run and itch and violent sneezing may occur. Your eyes may also start to water and you may get a sore throat.
The lungs and chest
Asthma can sometimes 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. Not all asthma is caused by allergy, but in many cases allergy plays a part.
The stomach and bowel
Most stomach upsets are caused by richness or spiciness in the food itself, rather than an actual allergy. However, foods which are most commonly associated with 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. It may also lead to failure to thrive. Some people cannot digest lactose (milk sugar). This intolerance to lactose also causes stomach upsets, but must not be confused with allergy.
Skin problems such as eczema (dry, red, itchy skin) and urticaria (also known as hives) often occur. Hives are white itchy bumps which look and feel like insect bites. Food may be a factor in some cases of hives and eczema.
Life threatening allergic reactions require immediate treatment
Most allergic reactions are mild to moderate, and do not cause major problems, even though for many people they may be a source of extreme irritation and discomfort. However, a small number of people may experience a severe allergic reaction called anaphylaxis. It is a serious condition which requires immediate life saving medication. Some of the more frequent allergens which may cause this are peanuts, shellfish, insect stings and drugs.
Effective prevention and treatment options are available
Allergen avoidance or minimisation relies on identifying the cause of your allergy and then taking steps to reduce your exposure to the allergen. For instance, many people are allergic to dust mites, therefore reducing dust mite in the house is important.