Strawberries trigger eczema through multiple routes. They cause mast cells to release histamine directly — a process called histamine liberation — which makes skin itchy and inflamed without involving a true allergic immune reaction. They also contain proteins that cross-react with birch pollen, causing mouth tingling in birch-allergic individuals.

The red rash that commonly appears around children's mouths from eating strawberries is usually contact irritation from the fruit's acidity, not a sign of allergy. Cooking destroys the birch-pollen-related protein, which is why strawberry jam tends to be better tolerated than fresh strawberries. White or pale strawberry varieties (such as pineberry) have very low levels of the main contact allergen and are often tolerated by those who react to red varieties.