> Do you too have no sense of smell?

That'd be the one: none at all. In fact I think I have even less than you - you say yours appears occasionally, but I've never had one, to the extent that I don't even know what it would feel like to smell something.

> and I have to say on the whole I'm usually glad when it fades away again :)

Yes, at school I tended to think I had the best of the bargain: the number of times I heard someone sniff and say "Mmmm, that smells lovely" I could count on the fingers of one hand, but the number of times per week I heard "Faugh, who's farted?" would have taken more than one hand most weeks :-) Mind you, these days I hear more of the former and less of the latter, so I'm no longer so sure.

The only serious problem it causes me these days is that it makes me very paranoid about gas ovens, because I know I don't have most people's early warning of gas leaks...

<madness>Lots of girls and lots of boys
Lots of smells and lots of noise..</madness>

I heard a thing on the radio a while back suggesting that loss of sense of smell can sometimes be viral - apparently it can be reversible and there's a support group somewhere on the web. Damned if Google knows where it is though :(