As a regular sufferer of headaches, I can report that there are seemingly endless causes of headaches of all different types/severity.
A few causes I frequently experience:
*dehydration
*tension in my neck muscles, caused by stress
*clenching my jaw for prolonged periods of time, caused by MDMA or LSD use, or stress
*not wearing my glasses for computer use/reading
*prolonged use the computer (even whilst wearing my glasses)
*low blood sugar levels
*lack of sleep
Do any of these seem like they could be the cause of your headache?? It could be your allergies but if you haven't experienced this type of headache with your allergic symptoms before it's unlikely to be the cause. Plus, I've had allergy headaches before and it doesn't sound like what you've described.
It actually sounds like your headache could be caused my tension in the jaw muscles, because I'm not sure if you're aware but the jaw muscles go up around the side of your face and connect to the skull on top of your head, i.e. where your pain began. Are you particularly stressed at the moment? Is there a possibility that you're clenching your jaw while you sleep, or subconciously while you're awake? Might be something to think about.
Remedies:
*first and foremost, drink plenty of water, at least 2L a day
*take some paracetamol or aspirin (sometimes this is enough to combat a headache for me)
*ask someone for a massage, or see a physiotherapist for a professional massage (they will also give you stretching exercises to do to alleviate the symptoms and prevent further tension build-up)
*get your eyes checked to see if you need glasses, or if you already have glasses, to check if you need your lenses changed
*if you think you're clenching your jaw/grinding your teeth at night, see your dentist
That should get you pointed in the right direction

If nothing helps or if it gets worse, please go and see your doctor.
Good luck! Headaches are the WORST!