Q I am a strict vegan. I eat a lot of seaweed to make sure I get enough vitamin B12, but am not sure exactly how much I need to eat. Can you tell me?

A We need vitamin B12 to make blood and help our cells divide. Our main source is animal products, so vegans can get low on B12. A deficiency is potentially dangerous and can cause irreversible nerve damage. But deficiency is surprisingly rare among vegans. One theory is that vegans may make a bit of B12 in their own guts. The other possibility is that you get some B12 from bacteria living in the soil that clings to vegetables you eat, but eating clods of mud attached to your veg may not be very appetising. A little B12 goes a long way - an adult only needs to take in two micrograms a day and children need half that. Babies can get B12 from breast milk and you can get it from vitamin supplements or fortified soya milk, cereals or meat substitutes. Seaweed and fermented soya, such as miso, contain an inactive form of B12 that humans find hard to turn into active B12, so I wouldn't rely on seaweed.

Hair there and everywhere

Q I am a 34-year-old woman with a very hairy chin. I also have dark hairs round my nipples and belly button, although it's the ones on my chin that bother me most. My GP did some hormone tests which were normal. She said that because my periods are regular, I probably haven't got polycystic ovaries and should rely on plucking the hairs out. Plucking gives me spots and of course the hairs regrow. What do you suggest?

A Lots of us have hair in places we would rather be hairless. There is rarely any underlying hormonal problem. Drugs such as steroids can cause hair growth, so check out any medication you are on. You are more likely to have a hormonal imbalance if you have infrequent or very heavy periods, difficulty getting pregnant, or a sudden increase in masculinity, such as your voice getting deeper or your clitoris growing. If you're overweight, losing a few pounds may help because male hormone (testosterone) activity, which is responsible for wayward hair growth, decreases as you do. Bleaching, plucking and removal creams are temporary measures, but most women settle for one of these methods. Electrolysis and laser hair removal are semi-permanent methods if you don't mind the cost and discomfort. Tablets can be useful but take a while to work, may not have the desired effect and wear off when you stop taking them. Oral treatments include contraceptive pills (Dianette and Marvelon), a water pill (spironolactone), a prostate-shrinking drug (finasteride) and a diabetes drug (Metformin).

Avoiding allergies

Q I have a dangerous peanut allergy. My first child is now six months old and starting to take solids. I'm not breastfeeding now. Should I give her soya milk instead of cow's milk formula to avoid allergies?

A No. Your baby may or may not inherit your peanut allergy. The best way to minimise her risk is to prevent her from coming into contact with peanuts for as long as possible, preferably until she is five. Most sources of peanuts are obvious but peanut oils can creep into many restaurant or precooked dishes. Children with allergies are more likely to have other allergic conditions such as eczema, hayfever and asthma. If your baby does develop eczema, avoid commercial skin creams, which may contain peanut oil, and use prescribed creams only. A survey of 14,000 babies in the south west found that of 49 children with a peanut allergy, nearly a quarter had been given soya milk in the first two years of life. The significance of this isn't clear but it seems sensible to steer clear of soya unless your baby really can't tolerate cow's milk products.

· 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.