What is an allergy?
An allergy or allergic reaction is what happens when your body's immune system reacts to something that is normally harmless. The substance that causes the allergy is called an allergen. Allergies can cause a wide range of symptoms that vary greatly in their severity. The same allergen can cause different symptoms in different people.

The most common symptoms caused by allergies are:

• runny or stuffed nose
• sore, red and itchy eyes
• coughing
• dry, itchy throat and tongue
• wheezing and shortness of breath
• diarrhea
• vomiting
• itchy skin or rash

Some of the symptoms caused by allergies can also be produced by other conditions. If you think you may have an allergy, it is important to see your doctor. The earlier you act, the more chance you have of controlling your symptoms.

The most common allergens (substances that cause allergies) are:

• alcohol
• bee and wasp stings
• bird feathers
• food (especially peanuts or other nuts, dairy products, fish and seafood, sesame seeds, wheat and citrus fruits)
• gluten intolerance (wheat, rye, barley or oats)
• house dust mites
• latex
• medicines
• mould
• nickel
• pets

Why do people get allergies?
No one knows exactly why people have allergies but you are more likely to have them if they are in your family. This is particularly true for asthma, eczema, hay fever and perennial allergic rhinitis. If you have one parent who suffers from allergies, you have about a one in three chance of being allergic to something. If both your parents are affected, the risk increases to two in three chances.

Why are more people developing allergies nowadays?
There are many theories about this, and much more research is needed, but experts agree that it has to do with the effect of our current lifestyle on the immune system. Allergies may be due to a combination of factors:

• our warm, well-sealed homes which harbor major allergens such as house dust mites
• the fact that so few people nowadays develop major infectious childhood diseases such as measles and mumps, which may offer protection against allergies
• a diet that is high in fats and low in fruit and vegetables
• the fact that we come into contact with many more substances than our ancestors did

Allergies may also be partly due to increased pollution from vehicle exhausts, although other forms of pollution have actually decreased.