Nowadays there are many food allergies and sometimes we don't feel well just because we have an allergy to certain kind of food.
Listening exercise to do: Are we afraid of food? (BBC 6 Minute English)
Have you ever seen the sitcom THE BIG BANG THEORY? Well, what is Leonard allergic to? Watch this and you'll discover it.
And what about Wolowitz?
And if you want to learn more English, here's: THE BIG BANG THEORY (English subtitled)
A couple of articles to read about the issue:
Food allergy and intolerance self-diagnosis (BBC, health)
Leave it out: are food intolerances fact or fad? (The Guardian)