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What Causes Chronic Allergies?

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What Causes Allergies to Start? continued...

The mast cells burst open, flooding the system with chemicals such as histamine. These chemicals cause allergy symptoms, like swelling. Swelling in your nasal passages might cause a runny nose. Swelling in the airways could cause asthma symptoms.

Keep in mind that the amount of exposure matters. If you're allergic to strawberries, maybe eating one or two never causes any symptoms. But once you eat three or four, you may suddenly break out in hives. There's a tipping point -- or threshold -- for people with allergies. You can handle some exposure, but if it gets to be too much, the immune system is triggered to attack.

Do Allergies Get Worse?

It's hard to predict how an allergy will develop. Some people -- most often children -- may outgrow an allergy completely. Others find that as they pass out of middle age and get older, their allergy symptoms become less severe. That's because the immune system weakens with age, and perhaps can't muster as strong a reaction to the allergen.

But usually, once you have an allergy, it doesn't go away on its own. And some people find that their allergies just get worse over time. That's especially true of allergies to foods, latex, or bee stings, which can result in more serious reactions with each exposure.

Obviously, external factors play a huge role in how allergy symptoms develop. All it takes is a heavy pollen season, or a new job in a moldy office, for allergies to flare up worse than ever.

Developing Additional Allergies

If allergy symptoms have worsened, there's another possible explanation. You might have just developed a second -- or third, or fourth -- allergy without realizing it. Anyone with allergic tendencies is at a higher risk of getting more of them. So if one year, your ragweed symptoms suddenly seem much worse, you might actually be reacting to another allergen that's also in the air.

Multiple allergies can interact in unexpected ways. For instance, up to a third of people with nasal allergies to pollens also have allergies to foods which have similar proteins in them, like vegetables and fruits. This is called oral allergy syndrome. You could have more severe allergic reactions if you're exposed to both at once -- say by eating a banana at the height of ragweed allergy season.

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