Allergy is a problem with your body’s immune system. In short, your body starts to treat a substance as if it is harmful when it normally isn’t.

In most cases, the allergen will be a protein of some sort. If you are allergic, your body will treat the specific protein as if it will be damaging. As a result, you produce a special type of antibody called IgE to attack the protein. IgE is a mediator in your body: this means that IgE leads other blood cells to release further chemicals including histamine. It is this internal cocktail of bodily chemicals which together cause the symptoms of your allergic reaction.

While this is what happens in general when you have an allergic reaction, it doesn’t explain why it would happen to you. The answer to that question is a complex one.  In fact, it is a complex set of factors that influence whether you will get allergies or not, including your genetic predisposition, your local environmental factors and the protein allergens that you are commonly exposed to.

According to Dr. Adrian Morris of the Surrey Allergy Clinic in the UK, you can blame a lot on your parents. A family history of allergy puts you at a much higher risk for allergies than the general population. Surprisingly, smaller families with fewer children are another apparent risk factor. If you are male, your chances of allergies are higher than if you are female. Obsesity is a risk factor. Even your mother’s diet while she was pregnant for you could affect your chances of allergy later. And then, there are the genes themselves:  chromosomes 5 and 11 seem to be involved in allergy predisposition.

It’s not just genetics that may predispose you up for an allergy later; it’s also the kind of environment that your parents provide for you. In fact, your first year of life sets the stage for much of what follows later. If there is cigarette smoke in your home, it can trigger allergy. Your diet as a baby, as well as early introduction of allergenic foods can have an impact. Air pollution, early use of daycare and early use of antibiotics can also promote the development of allergies.

Even your birthday can be a factor! If you are born just before the spring pollen season, you are more likely to be sensitized than if born at other times of the year.

However, you can’t get allergic to a substance without being exposed to it. For instance, you can’t develop an allergy to peanuts if you never encounter them! It takes at least one exposure for you to develop an allergy. So, your exposure is a final factor.

If you are an adult, you can’t change your upbringing! However, you can take steps to avoid allergens.