Penile pain

I have a painful penis. I sometimes have a mild pain when I ejaculate but otherwise can still enjoy sex. Sometimes it is uncomfortable to urinate which I do more often than usual. I have had urine and blood tests, a rectal ultrasound of my prostate which was horrible, and a battery of tests for sexually transmitted infections. Every test has proved negative. I think my GPs are sick to death of me but I am in despair. No one can tell me what is wrong, my penis still hurts and I find I'm checking myself whenever I can during the day and night.

You would be amazed how many men have so-called chronic pelvic pain syndrome, like you do. The pain is long-lasting and can be in the penis, anus or area in between. Mild urinary discomfort and pain while ejaculating are other typical symptoms. All tests prove to be negative in 95% of cases - the other 5% have infections in the prostate gland or bladder which can be treated with antibiotics.

Chronic pelvic pain often seems to start after severe pain from an infection, operation or accident. The pain causes anxiety and that may fuel the long-term problem. Some men may be more susceptible than others in the case of particularly sensitive pelvic floor muscles or a tendency for urine to reflux into the prostate causing inflammation.

Treatment is difficult. Avoid activities such as cycling, which make the pain worse. Hot baths are soothing. Regular ejaculation is good. Antibiotics such as doxcycline are often prescribed for a month at a time and can be repeated if helpful.

Finasteride, a drug that shrinks enlarged prostates, looks promising. Painkillers, antidepressants and counselling to deal with the pain and anxiety can help. There is a large research project on chronic pelvic pain under way in the US so expect progress on this up-and- coming subject.

Cold comfort

I'm particularly busy at work and travelling a lot. I want to stave off colds and coughs this winter. I had a flu jab and take vitamin C daily. Any other tips?

Vitamin C has entered popular mythology as a defender against many ills. But its fine reputation is largely undeserved with no consistent evidence that supplements prevent colds. Less than a gram a day probably does no harm, but larger doses can cause kidney stones and possibly have a negative impact on health by acting against antioxidants and causing cell damage.

Zinc may help reduce prolonged symptoms once you have a cold but is not proven to be preventive. Echinacea, derived from purple coneflower, is also widely available. It is said to stimulate the immune system.

The scientific trials are favourable though not unanimous. It may damage the liver and is best avoided in conjunction with other drugs - including alcohol - that affect the liver. Allergic reactions are possible and potentially serious. To avoid colds, you have to avoid people.

Losing it

My hair is falling out in the bath at an alarming rate and starting to look distinctly thinner. I'm a woman of 28 in good health - what should I do?

We shed hair all the time but it looks most obvious and alarming in the bath.Hair thinning is fairly often due to an underlying iron deficiency. It is important to have a blood test.

Iron levels can be low enough to cause thinning but not enough to cause anaemia. A simple full blood count, the standard test for anaemia, may miss milder iron deficiency. Iron supplements will restore iron levels to normal and may help your hair to return to its previous thickness.

• These answers are intended to be as accurate and full as possible, but should never be used as a substitute for visiting a doctor and seeking medical help. If you have a question for Dr Robinson, email drann@dircon.co.uk or write to her c/o The Health Editor, The Guardian, 119 Farringdon Road, London EC1R 3ER. She regrets that she cannot enter into personal correspondence.