Most people have a "completely preventable" severe headaches caused by taking too many painkillers, doctors have said.
According to them, some people are trapped in a "vicious cycle" of taking pain relief, which then caused even more headaches.
"Medication overuse headaches" feel the same as other common headaches or migraines.
There is no definitive UK data on the incidence of the condition, but studies in other countries suggest 1-2% of people are affected, while the World Health Organization says figures closer to 5% have been reported.
While painkillers would be many people's instant response, they could be making sufferers feel even worse.
Prof Martin Underwood, from Warwick Medical School, who led the NICE panel, said: "This can end up getting into a vicious cycle where your headache gets worse, so you take more painkillers, so your headache gets worse and this just becomes worse and worse and worse. It is such an easy thing to prevent."
Exactly how painkillers have this effect on the brain is unknown.
Most of the people affected are thought to have started with every day, tension-type headaches or migraines. The headaches then became worse as they treated themselves at home.
People with a family history of tension-type headaches or migraine may also be genetically more vulnerable to medication overuse headaches. They could be susceptible when taking pain relief even if it is not for headaches.
The new guidelines for doctors in England and Wales advise telling sufferers to immediately stop taking all pain relief. However, this will lead to about a month of agony as patients contend with regular headaches without pain relief, until symptoms eventually improve.
According to doctors, other options for controlling any underlying headaches, such as preventative treatments, could be considered.