Answer the following question given this paragraph: 

Most allergies can be treated with medicines. Medicines used to treat allergies include antihistamines and corticosteroids. These medicines help control the immune system when it attacks an allergen. Sometimes, allergies cause severe symptoms, a condition known as anaphylaxis‎. For example, they may cause the throat to swell so it is hard to breathe. Severe allergies may be life threatening. They require emergency medical care.


Q: Prescribed to treat allergies, antihistamines and corticosteroids help control what system that attacks allergens?


A:
immune system