Sneak a glance into "worst and best" allergy causing foods

In an allergy, the immune system shows an abnormal reaction to a harmless trigger in the environment, and ends up releasing histamine, a “protective” chemical. The reaction leads to a production of symptoms, we term as allergy. Lots of times people can target their triggers and are on guard against them, but what if one is unaware that the trigger may be a food stuff they regularly sink their teeth into and roll their tongue around:

An apple and fruits