DEAR DR. DONOHUE: I would like some help with a problem. I suffer from cluster headaches. I have been to doctors, and they offer no help. I tried oxygen without any luck. Everyone talks about migraine headaches but never cluster headaches. – S.L.

ANSWER: Cluster headaches occur on one side of the head and usually behind an eye. They produce fierce pain, and they often come on during sleep. Many times the nostril on the side of the headache drips, and the eye on that side waters.

These headaches can wake their victims, who jump out of bed to frantically pace the floor in an attempt to get rid of the pain. This is the exact opposite of migraine sufferers, who seek a quiet, dark place to relieve their headaches. The pain lasts from 30 to 60 minutes.

Cluster headaches have the habit of recurring from twice to six or more times in 24 hours. That’s the “cluster” in their name. They can occur daily for weeks or months and then suddenly fade away for months or years before resuming another cycle.

There are many ways to treat cluster headaches. Oxygen is one of them. How were you taking it, and for how long did you use it? It should be delivered through an airtight mask, and you have to breathe it for 10 to 15 minutes. Imitrex, a migraine medicine, is also used for cluster headaches, and it comes as a nasal spray or as a self-administered injection. Those routes make for a quick response.

Have you tried preventive treatment? Here are some medicines to take when you don’t have a headache to keep one from happening: Calan, a heart and blood pressure medicine; Neurontin; lithium; and Amerge.

You have enough information to talk with your doctor about trying things you have not yet tried.

Readers who would like more information on headaches can order the headache pamphlet by writing: Dr. Donohue – No. 901, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: The doctor found a trace of blood in my urine by microscopic exam. The urologist has said there are no tumors in my kidneys or bladder. I asked if this will get worse, and he said rarely. I am 67 and have never heard of this. Will you please comment? – J.L.

ANSWER: The finding of urine blood, either visible or detectable only with a microscope, sends an SOS to look for cancer. Cancer is not its most common cause, but it is its most serious cause. X-rays, scans, ultrasound pictures and looking at the bladder wall with a scope are some of the ways to ferret out cancer. You have a clean bill of health in this regard.

Infections are another cause of blood in the urine. They are easy to discover. Inflammation of the kidney – glomerulonephritis – is another cause of urine blood, and lab tests can bring it to light.

Some inherited conditions that are not much more than oddities announce themselves with urinary blood.

Your doctor has looked for the important causes of hematuria, as blood in the urine is called. None was found. You can relax.

DEAR DR. DONOHUE: I am 83, and my right testicle has become quite enlarged. There is no pain, but it is uncomfortable at times. What is this, and how do you take care of it? – J.M.

ANSWER: Most likely it is a hydrocele (HIDE-row-seal). Each testicle has a double-layered covering. When fluid collects between the two leaves of the covering, a balloonlike swelling can be seen. In a dark room, light from a flashlight placed on the back of the testicle shines through the front of it if you have a hydrocele. If hydroceles are not painful or are not very large, they can be left alone. However, don’t let the matter rest here. See your family doctor for a confirmation of this guess.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.