Breakdown of Mam alergię na orzechy.
mieć
to have
na
on, at / to (motion toward) / for (a meal) / for (waiting for)
alergia
allergy
orzech
nut
Questions & Answers about Mam alergię na orzechy.
Why does alergia change to alergię here?
The verb mieć (to have) requires its direct object to be in the Accusative case. Since alergia is a feminine noun ending in -a, that ending changes to -ę in the Accusative.
Why do we use the preposition na instead of a word meaning "to"?
In English you say you are allergic "to" something, but Polish uses the preposition na (which usually means "on"). The fixed phrase you need to memorize is mieć alergię na.
What case is orzechy in this sentence?
It is in the Accusative case because it follows the preposition na in this specific phrase. For non-human plurals like orzechy (nuts), the Accusative form is exactly the same as the basic Nominative plural.
Does orzechy refer to a specific kind of nut?
Orzechy is the general word for all nuts (the singular is orzech). If you need to warn someone specifically about peanuts, you would say orzechy ziemne (literally "earth nuts").