Having an onset of severe headache can ruin your activity, and place yourself in danger. Stop and ask yourself why are you NOT feeling as usual.
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Consider recent activity just before headache started, and what task you are now doing. These are some steps on how to relieve a headache quickly:
Be aware of your discomfort, and that the severity may become unbearable.
Think about what you were doing prior to pain, blurred vision, nausea, sensitive to strong light, and current activity.
Slow yourself to better allow your body to adapt to current/changing conditions safely.
(Keep your FRS or cell-phone handy!) Consider your intake of water, and food in past 3-5hours, and if you consumed your regular medicines completely and in proper amounts.
If able, slow yourself to allow blood pressure to lessen, and avoid bending or stooping.
Maintain your breathing in slowed but adequate manner for current activity.
Keep yourself in reclined position, or relaxed sitting position, for 10-15 minutes.
Test yourself at intervals if any movement makes headache worse, leaning forward and to sides, checking your balance, and symptoms should begin to clear.
Make use of your day-pack supplies for water or protein/snack bar.
NEVER be ashamed to tell your group that you are having problems, and where your emergency medicines are stored.
(KEEP IN MIND: The effort and time to return to your transportation point!) PLAN WELL and the blessing of your trip will also be a positive one.