Last Wednesday I ate my first peanut for over 15 years

In my early 20s I was part of a second-stage trial for Beconase, a nose spray that helps with hay fever. To test I was suitable for the trial, ie that I did actually have hay fever, I had a skin prick test. This showed I was indeed allergic to grass.

However, for some reason they also tested peanut, which came up positive. I was handed a pamphlet which warned of the danger of 'anaphylactic shock'. This is a severe reaction to peanut which can kill in minutes.

Of course, I was very worried about this and immediately cut all nuts out of my diet.

Over the years I've had various tests to determine what exactly I'm allergic to, both skin prick tests and blood tests (RAST) but they've all been inconclusive. Finally I decided that the only real test was an 'oral challenge'.

I had yet another skin prick test at Adenbrookes hospital in Cambridge, and convinced them that I needed to do the oral challenge. After a bit of a wait, I found myself back at the allergy clinic last Wednesday, feeling very apprehensive. Obviously they're prepared to treat anaphylactic shock with adrenaline, but I was kinda worried...

I was treated very well at the hospital, everyone was friendly and the doctor explained everything step by step. We did more skin prick tests, a blood pressure test, a 'blow hard down this tube' test and had a chat about my history and the test to come.

First, I had to rub a piece of peanut on my outer lip. If I was severely allergic to peanut, I would have had swelling. After 10 minutes, there was no reaction, so we tried inner lip, then tongue. As I'd not had a reaction at all, they gave me a slither of peanut to eat, then a quarter, then a half, then a whole peanut!

I did feel that my throat and palate were raw and uncomfortable, but the doctor was not convinced this was an 'oral allergy' (see below) as that's rare with peanut. It was more likely that because it's hay fever season and my throat was already sensitive, that the scratchiness of the peanut was irritating.

In fact the doctor said she'd not expected any reaction, looking at my test results/history, but it was as important to prove a negative as it was a positive.

Apparently the understanding of allergies has come a long way in 20 years. It's now clear that there is an 'atopy' or allergy gene. This leads to sensitivity, which is seen as small reactions to skin prick tests (up to 3mm diameter wheal) to various substances. These small wheals are now seen as *negative* results as they do not indicate a full allergy.

These small wheals were what had been so confusing over the years.

Now, my reaction to peanut was 6mm, so it was technically a positive, but thinking about it, you only get anaphylactic shock the second time you eat peanut... if you don't get it then, you're not going to, which is why the doctor wasn't too worried about me. Of course I could have had some other reaction, but it was never going to be fatal. Also, I found out that wheals can be up to 30mm, so a 6mm wheal wasn't a large reaction anyway.

Now, my reaction to hazelnut was 8mm. The doctor thought I might get 'oral allergy' reaction to hazel, which is, basically, an itchy mouth. Hazel and apple share common enzymes with Silver Birch, which many people, including me, are allergic to - along with grass, that's what gives me hay fever. When I eat raw apple I get an itchy mouth. This was rather confusing to me and my parents as a child! The good thing is that cooking apples destroys the enzyme, which means I can have apple pies without any problem. However cooking nuts doesn't destroy the enzyme, which is why the doctor thought I might have an oral reaction to hazelnut - I'm going back to Adenbrookes at some point for another oral challenge.

For all other nuts, the advice was that I am unlikely to have any reaction to them, even for those where I get a small wheal on the skin test - it will be safe for me to self-test at home, eg test outer lip etc.

It's been a huge weight all these years, not knowing exactly what I could/couldn't eat. It turns out it was an unnecessary worry. I actually broke down in the hospital because it was such a huge relief. I wish they'd never done the test in the first place, but I can't get too rilled about it.

So, why has it taken me a week to blog about it? Well it's difficult to get too excited about a negative result, even if that's really good. Nothing has changed in my life. I suppose I could now lick my fingers after making a Nutella toast for Leon, but being careful is so ingrained that I don't.

The big change will be when we go to Holland. Christine is going to want Saté sauce on her chips, and I guess I'll try it. Still fills me with fear, even though I know now nothing will happen.

It's a big change which I'll slowly get used to. Can't wait to eat pistachios again, my favorite nut, yum yum!!!