Notalone - what a sad story. I am so sorry. The whole nature/nurture thing is fascinating. My own mother had (has) no problem with sick, and was always very kind to us when we were ill (my sister had a lot of sick bugs as a child - she specialised in getting them on Christmas Day!!), so she can't have passed the problem on to me (and my sister has never been bothered by v-ing). And as I've said before, my DS is terrified of v-ing (either doing it himself, or being around someone else who's done it), whereas DD couldn't care less either way. My Mum does say I've always been prone to anxiety and obsessions, which is true (at around five, I was so terrified of the house burning down that I made an escape ladder out of my clothes - yes, very useful!!) I am a bit obsessive about antibacterial spray, but that's about as far as any kind of cleaning obsession goes. But I am certainly given to anxiety, especially now that I have the children to feel anxious about (at the moment, I can't believe I'll ever let them cross a road alone, or go in someone else's car, never mind walk to school on their own!!! I can't read any book in which a child comes to harm, as it sends me into too much of a tizz...) So perhaps I'm genetically prone to anxiety, and have passed the gene on to my poor DS as well.
So far as food is concerned, I'm always chucking stuff out just in case. It drives DH round the twist!
If I could find a local hypnotherapist that I could afford, I'd probably be tempted (if a bit afraid that he'd either dredge up something horrible, or that it wouldn't help at all). I think I will try CBT, though, especially if you can get it on the NHS. It seems that it won't 'cure' the phobia, but it might make it easier for me to live with it - and I'd be grateful for that at the moment.
Back to the dreaded topic: we went to a party in a park after school today. I decided it would be a safe bet as it was outside - but, of course, there were buns and crisps which all the children were helping themselves to (and so was DH, to my horror). There is no way those children had washed their hands. Then I heard one of them saying he felt sick. Aaaaaaaaargh. I shall be really obsessively checking the children and DH for symptoms for the next 48 hrs.