The common way to treat mild allergies is giving antihistaminergic drugs and/or steroids (such as fluticasone).
I understand that adrenaline can also be used, and is used, mostly for severe, emergency allergies, via Epinephrine (adrenaline) autoinjector also known as EpiPen.
From Wikipedia (Epinephrine (medication)):
It is given intravenously, by injection into a muscle, by inhalation, or by injection just under the skin.
Why is adrenaline typically not prescribed as pills (tablets/capsules)?