Does your nose close up when you have a cold drink? Or do you start to wheeze when you eat pickles? You could be suffering from an undiagnosed preservative allergy.

Like all armed forces, your immune system makes mistakes. In real life it's called friendly fire. In your body it’s called an allergic reaction. Learn more about this mechanism.

More people are allergic to cats than dogs. However, a new study shows dog allergens are more ferocious irritants to asthmatics than cat dander, cockroaches, mold and dust mites.

Often it is difficult to distinguish between an allergic reaction and say, the onset of a cold. There are also many different allergens that can cause an allergic reaction.

Allergic reactions to drugs are fairly rare, but almost all drugs can cause a reaction of sorts in a small number of people. Drug reactions ranging from a mild allergic reaction.