Dr Tom Smith answers your health questions

Can being cold and wet give you a cold?

Question: Last week on the way to the cinema I got caught in the rain and, thanks to leaky boots, my feet got wet. Two days later I was struck down with a cold. Are the two directly related?

Answer: They aren't supposed to be, but cold experts have argued the point for years. Their current position is this: being in cold weather doesn't put you at any more risk of catching a cold than being warm. Lowering your core body temperature, however, may lessen your immune response to a viral invasion, so having wet, cold feet may have made you a little more susceptible to infection. My Scandinavian friends say there is no such thing as bad weather, only bad clothing, but there is an ongoing argument about that, too. What isn't arguable is that sitting in a cinema with cold sufferers around you will put you at high risk of catching a virus, regardless of your body temperature. All it needs is one sneeze nearby and you have your next cold. Two days is about the right incubation period, too.

How much salt is too much?

Question: How strict should I be about my three-year-old's salt intake? I try to keep it down to a sprinkling to flavour cooking, but he always wants extra on his food. What is an acceptable daily intake, and what harm can it cause if it's exceeded?

Answer: The salt in your cooking should be enough for him. It's hard to relate grams of salt per day to the amount actually swallowed in food. If you wish to avoid giving him too much, offer other spicy tastes instead. If he insists, then one shake of the salt cellar is probably enough, provided the holes aren't too large. Some (now quite old) studies found that people shake the cellar the same number of times regardless of the size of the hole, so they get different amounts of salt with different cellars, but they don't even notice. For a normal healthy child, a little extra salt won't do any harm. Overloading with a lot of salt could lead to fluid retention and high blood pressure, but this is unlikely with a normal diet. If you and he can cooperate over a month or so to reduce his salt intake, he may get used to the new low-salt tastes and lose his desire for extra salt altogether. It's an acquired taste that can be unacquired.

The truth about antibiotics and booze

Question: I've always believed you should never mix antibiotics and alcohol, but I've been told it isn't harmful. Is this true? If not, what are the risks?

Answer: You can take alcohol with most antibacterial agents (that includes antibiotics - agents developed from biological substances, such as penicillin - and synthetic antibacterial drugs, which are not strictly antibiotics). However, some antibacterials, the most notorious of which is metronidazole (used a lot in dentistry and bowel infections), do react badly with alcohol and make you very sick. If you're prescribed an antibacterial drug, ask your doctor if you can take alcohol with it. Most of the time you will be able to do so.

Should I have the snip

Question: I'm a 35-year-old man with two children and am considering a vasectomy. Is it reversible?

Answer: It is meant not to be, so don't have one unless you're sure there's little chance of you wanting more children. That said, most vasectomies can be reversed (the sperm-carrying tube, the vas deferens, can be made patent again). But doing so after some years is no guarantee of fertility.

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