Thursday, February 18, 2010

Wait, I'm allergic to honey dew?

Interesting case the other day....

Patient tells me everytime she eats honeydew, her mouth and throat start itching and she thinks she's allergic.

We do skin testing and ragweed pollen is very positive.

So what's going on?

This something called Oral Allergy Syndrome. It's most common with people who are allergic to birch pollen who eat tree fruits, like apples, pears, and cherries. Basically, a protein in the birch pollen cross reacts with proteins in these tree fruits. Similarily, honey dew cross reacts with ragweed pollen.

There are lots of other examples including:
- zucchini and ragweed
- asparagus and ragweed
- fig and grass

These proteins are denatured with heat & cooking the fruit or vegetable prevents to allergic reaction. In some people, just peeling the fruit or vegetable will solve the problem, as most of the allergenic proteins are located in the skin.

In most cases, people with oral allergy syndrome won't progress to anaphylaxis, however, we still recommend avoiding the offending food, unless it's cooked.

There is some evidence that immunotherapy with the cross reacting pollen can help treat oral allergy syndrome, but we still need more data.

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