You can get rid of a headache by resting, getting a massage, visualizing peacefulness or by using heat or cold depending on your preferences. Drink plenty of water and eat properly and regularly. You should also get enough sleep, exercise and fresh air.
My allergies give me awful headaches and have my stomach feel odd -- sometimes hungry, somtimes nauseous. If you feel it's necessary, take an allergy pill, eat something small-to-moderate, and take a cat-nap. Isolate yourself from loud sounds.