Allergies occur when the body perceives a harmless foreign substance as a threat. An "allergen" (as the substance is known) - for example pet dander or dust mites - triggers a reaction from the body's immune system. Basically, if the immune system falsely identifies a safe substance as dangerous, it attacks.
Symptoms can range from annoying to deadly
Common allergy symptoms such as sneezing, coughing, runny nose, sore throat, diarrhea, vomiting, itching and hives are all the body's attempts to dispel the offending allergen.
Anaphylaxis is a severe allergic reaction that, although rare, can cause difficulty breathing, leading to shock and even death. It may begin as soon as contact with the allergen is made, either through inhalation or through touch, and it affects two or more body systems, such as respiration (breathing problems) and circulation (swelling). The first exposure an individual has to the offending allergen is often unknown to them, but the body builds up sensitivity before eventually reacting with anaphylaxis.
If anaphylaxis progresses to anaphylactic shock, emergency treatment is needed. A shot of epinephrine (synthetic or animal adrenaline) can reverse symptoms if it is administered almost immediately.
People who have asthma as well as allergies are more likely to have an anaphylactic episode.
Treatment of allergies
Unfortunately, for most people the most effective way to deal with allergies is to avoid the allergen altogether, be it animal allergies from the dander on your cat Fluffy or that milk chocolate you crave so much. Avoiding the trigger can be harder for food-allergy sufferers, who have to pass up any processed food that was made with a certain ingredient or that might have come into contact with it.
How to make your home allergy friendly
Particularly with dust mite and animal allergies, symptoms can be greatly diminished through air filtering. Frequent cleaning with HEPA vacuum cleaners can reduce allergens, including dander and mites, helping allergic individuals better cope in the home environment. It will also allow guests who are allergic to your pets to stay for a while when they come to visit. Keeping humidity levels from getting too high by using a dehumidifier is a great way to stop the proliferation of dust mites, which need a lot of moisture to survive.