This is the 9875th most frequent Polish word.
alergii
"Allergy."
The word 'alergii' is used here in its dative form 'alergię' as the object of the verb 'mam' (to have), indicating ownership of the condition of allergy.
Mam alergię na pyłki kwiatów.
I have an allergy to flower pollen.
In this sentence, 'alergii' (genitive singular form) is used to indicate possession, relating the symptoms to the allergy.
Objawy alergii czasami są bardzo dokuczliwe.
Symptoms of allergy can sometimes be very troublesome.
Here, 'alergii' is in the dative case, reflecting direction or purpose, as the medication is taken to counteract the allergy.