Well, I can tell you precisely what causes them and what doesnt. And a good natural remedy for it as well. I smoke my harry (brown) and in my country we only get the purest of the stuff since we do border the Afghans. So it is not the cut. And it is not cotton fever. And today I used some, hardly anything much after 6 months and got the headache after about 3 hours. So it is also not regular use. However, what it is is a combination of dehydration, over stimulation of receptors, light and noise and blood pressure build up in the brain. When you are regularly on smack you tend to live in a state of dehydration and dont notice how badly you need water. So when you get the headaches it comes as a shock. Also, with fairly regular use, whether it was years ago or currently, the opiate receptors in the brain grow and it is easy to over stimulate them even after years of a clean patch. They dont go away but just become inactive. Light and noise are not main factors but contribute, such as using a laptop, listening to heavy music, reading a book which is straining. And please note that heroin does not cure headaches. It is a painkiller for the entire body neck down. Blood pressure usually builds up with heroin use as you warm up for the dope. And so, to counter this hellish pain here is what i do, and it works. But might take an hour or a bit more to get back to normal.
Firstly, before during and after use drink A LOT OF WATER. ALOTTTTTTT!! like ALOOOOOOTTTTTTTTTTTTT of it. The internal heat heroin provides exhausts the water in the body, almost as fast as you can drink a stable flow. So drink a liter of water before use and about two more during the next few hours.
Secondly, Dont try to cure this headache with more harry. You will seriously regret it when youre in bed unable to move without screaming.
Thirdly, avoid bright lights and loud noises and try not to use the laptop excessively or to read a small font. The strain on the eyes can really be a contributing factor.
And lastly, try to counter the pressure on the brain vessels with some aspirin which also is good for headaches in itself. I take a regular does of aspirin with 500mgs of paracetamol when i start to feel the headache coming on. Then i go to my bed and lie down for an hour while i keep sipping water. A VERY VERY IMPORTANT POINT HERE IS to breath deeply. Heroin causes respiratory depression and not enough oxygen is getting the body with your doped breathing pattern. I like to breath in through the mouth and out the nose. After an hour it is 80 percent better. Follow this with a cup of tea or coffee for a caffeine boost to feel absolutely normal again.
I know this is a lot to do and can ruin the buzz, but it's like getting a blow job compared to the headaches we get. Once again I would like to stress on drinking as much water as possible and taking long breathes. Even when your stomach is full of water and you can hear it swirling around, you will notice dried lips or a parched mouth. Thats how much heroin can dehydrate... And the leading cause of headaches along with the best cure for it is said to be water shortage and hydration. Oxygen and water are no doubt the best remedy for Heroin Headaches.
Hope this was helpful.
Oh, and to avoid heroin hangovers the next day, drink as much water as you can hold down before going to bed and if you do wake up somehow during the night drink as much as you can again. If you manage to cure your headache, dont stop drinking water. The pain will return if you do.
-Jelly
P.S. Some say it is due to Intercranial Pressure, but i disagree as ICP causes quite a few symptoms that do not show up with heroin headaches. But there definitely is some pressure on the head with heroin use. Avoid hard pillows or neck support for a better flow of oxygen via blood to the brain.