The answer to this centres around a pigment called melanin. This is a pigment that gives us dark moles, dark skin and dark hair. This is called eumelanin, and there's a slightly lighter version called phaeomelanin, which gives people red-ginger hair. Everyone has genes in their DNA that will give them different levels of these two pigments. So people who have very light and blonde hair don't have very much of these pigments at all. As your cells get older, they will change the way that they use their genes. If you have a child born with very dark hair and then becomes blond, this would suggest that the gene that's making melanin when they're a baby has been turned off. If a child is born with blond hair and becomes dark, it's because genes have started turning on melanin pigment. So it's not fixed, and even later in life you can go from being a blonder person to a darker person.

That's a really important question, because carbon monoxide is a gas that's produced when carbon fuels burn but don't burn properly. It's very poisonous and can kill people while they sleep, so it's great that you're thinking of installing a carbon monoxide detector. What you need to know is whether carbon monoxide is lighter or heavier that the rest of the stuff in the air, which is mostly nitrogen and oxygen. The answer is that carbon monoxide is lighter. What you need to do is put your detector either high up on a wall or on the ceiling. However it should be kept 6 to 12 inches from the corners.

I'm not sure it's true that people with worms are thinner than people without worms. In fact the person who brought the worms back from New Guinea was the fattest person in the lab and still is despite the fact he's still carrying 300 worms. The other interesting thing related to worms and connected to the previous caller from the States is that they give you an insatiable appetite. When you have these hookworms, you just can't stop eating. Whether you put on less weight despite eating more, I'm not too sure. But I don't think that people are thinner if they had worms, so it probably wouldn't work on fat people.

There are a number of reasons why we have gas in our guts. Some of it's just air that we swallow, which contains nitrogen, carbon dioxide and oxygen. The rest of it is made when undigested food and a sugar called lactose passes through into our large bowel, and bacteria start eating the sugar. The bacteria produce quite a lot of smelly gases, especially if the food has quite a lot of sulphur in it. This would include food like cauliflower, eggs and meat. Beans are particularly fart-o-genic, and although they don't make bad smells, they do make you produce quite a lot of gas. This is because beans contain quite a lot of sugars that humans can't digest, but bacteria love them! When you get worm infections, it actually increases your level of flatulence. This is being published in a scientific journal very soon.

I'm glad you asked that question Peter because my lab is also looking at the effects of maggots in wounds, and we've identified a number of enzymes that maggots use to digest dead and dying tissue to kill bacteria. The same enzymes promote tissue regeneration. So in fact, maggots are actually very good tissue engineers and repair tissues through their secretions. Maggots only eat dead tissue because it's already digested, and they only stay in the wound for three days. The flies then fly off. The latest development is to put the maggots into a nylon tea bag, rather than have them 'free range'.

The trial we have conducted to date was a safety trial where people were infected with graded numbers of worms. They went from 10 to 25, 50 up to 100. If you give somebody 100 worms, they do not feel well. In that case we had to take the worms out of the system as quickly as possible. You're right to ask this question because we need to be careful not to give too many worms at one time. They itch when they go through your skin, but you don't notice anything again until they reach your gut. I had 50 and it gave me a dull ache under my ribcage.