Anyone had a negative skin prick test but still been allergic?

[calvemjoe]

DS(3yrs) had a massive reaction to egg at 9mnths and a skin prick test confirmed his allergy. He had a negative test about 10 months ago but we haven't reintroduced egg as he has persistant dihorrea and it would be difficult to tell if he had any reaction.
Anyway my dad got him to help mix marie rose sauce (with mayonaise) and within minutes he was covered in hives, wheezing and swelling up. A repeat skin prick test came back negative, although the positive control reaction only 'measured' 1mm and was invisible to the naked eye. On the strength of the skin prick test ds has been discharged from his consultant. I'm feeling a bit let down and wondered if anyone else had had a -ve test but was still allergic?

oh no - surely the reaction that your son got should have meant a lot more tests at least, in case he is allergic to something else?

I had a different sort of allergy test, it was experimental, done by Dr Ray Choy (he has published stuff about alternative allergy tests, you can find it in the internet). It was pretty accurate though (later confirmed by skin prick tests). Can you try to get another sort of test done, to see if the results are the same?

The only other times I have heard of when a skin prick test came back negative was when it wasn't a genuine allergy (eg reaction to azo dyes) but that wouldnt seem to be the case here.

Yes, my DS had a negative skin prick test to egg at Addenbrokes allergy clinic, yet two days later he had a reaction (swollen mouth, vomiting) to egg. As far as I am aware, false negatives for this test are rare (can't remember the exact figures but I think the test is around 98% accurate) but not impossible. Next time I'm holding out for RAST tests!

I've managed to get him booked in for a specific Ige test on tuesday, but was advised that the test is not as acurate. Can't believe they just dismissed him.

You might want to print off and take this.

www.allergyuk.org/allergy_skintest.aspx

I've heard of children having negative skin prick tests and then anaphylactic reactions. There is no way he should have been discharged with such a small control reaction. Had he had any antihistamine in the previous days as that would invalidate the test?

A sensible doctor would arrange a blood test and possibly a food challenge before discharging a child with that history.

I'd guess this was a paediatrician "with an interest" in allergy?

I'd specifically kept him off piriton even though his hayfever had kicked in, he'd had medised before his previous test and I was concerned it had effected the results. It was the diet specialist that agreed to the blood test, we were not even given the chance to talk to the consultant, just ushered out. He is supposed to be an allergy specialist.
Thanks for the link.

I'm confused. How long does IgE remain in the body for? Would he need to have a recent reaction for the test to pick it up? I'm not going to feed him egg, I just wondered how it works.

want to name and shame? Then we can find out if he really is an allergy consultant, there are very few of them. Who ushered you out - could it have been a junior doctor who needs a bit more training?

Antihistamine affects skin tests but not blood. We tried asking about the blood test but the answer didn't make much sense. I think it meant that when they expose his blood to a bit of egg it will react if he is allergic to egg. It doesn't matter if he's had a reaction recently because they will in effect provoke a reaction - in his blood but not when its in him. Once again its not fool proof because sometimes people react to food only when its in their digestive system. Only 100% reliable test is a food challenge. However it sounds quite likely his blood test will be positive and then you may be going back to the consultant.

DS skin prick test for milk came negative, but he stills get bloated, face puffed and complains of pain immediatly after he has it.

"I'd specifically kept him off piriton even though his hayfever had kicked in, he'd had medised before his previous test and I was concerned it had effected the results"

Somebody mentioned in another thread about Medised being as good for allergies (or even better) than Piriton so... If this is true, I'm very much afraid that it may have affected the test results.