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What is a RAST test like?

(14 Posts)
NicknameAlreadyTaken Sat 20-Jun-09 12:12:00

I suspect my DD (17mo) is intolerant to dairy. I'm pretty sure there's also something else, but haven't yet detected what it is because she has also been reacting to things i eat (i still BF her a lot), and so it's pretty complicated. sad
We were given a referral to an IgE + RAST test for dairy.
What is this test like? Do they just take some blood from your vein? And if so, how much do they take?
The problem is, DD has been very fearful, but now seems to be slightly on a mend, so I'm not sure it's the right time now for any blood tests, as she will definitely be scared to death and that will most likely make her become more fearful again (we already had a similar thing when she twisted her ankle and spent half a day at A&E crying herself out when we tried to get her ankle x-rayed)

NicknameAlreadyTaken Sat 20-Jun-09 12:20:48

Oh, yes, and do I need to give her any dairy before doing this test? She's been off dairy for many months (and so have I).

And one more question, sorry! It says on the form 'RAST - cow's milk protein'. What if we also wanted to check say, potatoes, or something? Is it something we can ask for when we come for the test? Or do we need to request it with paed?

girlsyearapart Sat 20-Jun-09 18:40:04

hi we had RAST test done on our 8month old a few weeks ago. i went to the test with my husband as felt needed moral support! needn't have worried. there were three nurses doing the test and one of them had the sole responsibility of entertaining and distracting the baby while the blood was drawn. She had a big box of toys and although it took several attempts to draw the blood my girl didn't even flinch let alone cry. (although I felt like crying!) We were initially there to test for dairy, egg white & yolk, tomato, wheat and banana. After the test the nurse said there was enough blood taken to test for more and asked if I wanted to add. So we added strawberry, plum and dog hair(dander) We already pretty much exclude all those from her diet on medical advice but weren't told specifically to avoid due to tests. The only thing is I've been told the results aren't definitive just indicators of high or low allergy possibility. Results back beg july. I know a lot of what i've said is dependent on what your testers are like but you could always buy your child a new toy or something to soften the blow Sorry this was so long! good luck.

DesperateHousewifeToo Sat 20-Jun-09 18:54:09

Yes, basically, it's a blood test.

Usually, they will put some anaesthetic cream on the back of the hand covered with a plaster for 15 mins beforehand to numb the area.

Play thereapists are often used to distract and can do so very successfully when they are little. It's since ds has been older and has known what to expect that he has been upset by it. The first couple of bloodtests he had, he did not even notice.

They may let you breastfeed at the same time if it calms her.

With regard to adding allergens to test for. Ds' consultant is always reluctant to add too many as he says they sometimes don't have enough blood and then only test a couple of them - sods law, then missing out the really important ones!

girlsyearapart Sun 21-Jun-09 07:17:40

Not sure if they have to be a certain age for the anaesthetic cream? When we were in the waiting room there were two other children who were about 5 ish and they both had it but they didn't put any on the baby. Not sure if it's age related or maybe the other kids were having different tests?? DesperateHousewifeToo- what kind of results did you get? Were they conclusive? How often did you get re tested and have you also had skin prick tests? So many questions...

tatt Sun 21-Jun-09 09:15:10

what are her symptoms? I ask because a RAST will only detect allergy, not intolerance. If your child has allergy symptoms then they need the test, intolerance and it's grief for nothing. Gps don't get much allergy training and may not know the difference. If you've been referred to a consultant paediatrician they may still get it wrong or feel they have to test for allergy if asked.

There are 2 different types of anaesthetic used in clinics I've attended - spray or wipe and cream. Spray is quick, cream is slow but more effective. We had to ask for the cream.

No results are conclusive but RAST tests are pretty good.

NicknameAlreadyTaken Sun 21-Jun-09 12:31:27

Thanks for answers, everyone! It's more or less clear now, but I guess you are right, it alsso depends on personnel we'll be dealing with. And as for entertainment, it sounds worrying to me rather than reassuring because DD is still pretty wary with strangers, especially when they are loud and bubbly (which is exactly the way many people try to entertain babies smile)

tatt, I'm not an expert in allergy, but I thought it's more likely intolerance rather than true allergy she's having. So, giving it another thought, you might be right and this test is then useless for her as intolerance has nothing to do with immune system reaction which is being checked by this test (as far as I know now, having googled for more details on it blush). But you know, i'm not a doctor and the paed who ordered this test for us should (in theory) know better!
I guess many of us are becoming better allergy specialists than our drs! wink Just because they often don't have a clue, so we need to get information ourselves... sad

DD won't get symptoms quickly, it can all show in a few days depending on the amount of dairy she's eaten. Last time I tried, I was giving her some grated cheese in every meal for about a week. At first she seemed fine, but in a few days she got worse and it took her a week or more to recover after I stopped giving her cheese. She would have a lot of gas and loose poo, broken sleep at naptimes (would sleep just half an hour to an hour instead of 2-3 hours of her normal nap), be generally more tired and irritable, feed much less (both BF and solids). Sometimes she would also get a rash on her bottom at the same time which would be pretty difficult to get rid of (Metanium is the only thing that helps but it still takes a while)

BTW, can all this be a sign of simple tummy bug as they call it (a result of putting dirty hands into mouth on a playground or something)? Because she's been off dairy for quite a while but would get similar symptoms (without gas though and not so acute, for shorter periods, etc) from time to time, so I thought it could be something else she's reacting to, but couldn't quite get what it was. So, is it all being caused by a plain tummy bug? hmm

I asked my GP to refer us to an allergy specialist, but I suspect the dr we saw might have been an ordinary paed because some of her comments contradicted to information I saw on allergy-related sites.
I didn't explicitly ask for this test, just asked her whether there were any tests that could help us finding out whether she's indeed reacting to dairy. And at that time she told there was no test that would give a definitive answer, so she just refered us to a dietician, but then a letter came from her saying she thinks we need a test.

girlsyearapart Sun 21-Jun-09 13:27:56

The "play lady" we had wasn't one of those wacky loud people she was really unassuming and seemed genuinely caring. Really does depend on where you go though doesn't it??
Tatt- her symptoms for dairy, wheat, banana and tomato are severe worsening of excema looks like her face has been burnt only an hour or so after eating. Also had some projectile vomiting of normal formula. Many other foods make her area round her mouth red which we've told to help by putting vaseline around her mouth before eating.Haven't tried it yet though. Only thing with a different reaction was plum. Less than a quarter of a small plum brought her up in red hives top to toe.

tatt Sun 21-Jun-09 17:49:41

NicknameAlreadyTaken the paediatrician we saw was not well informed, fortunately we had previously seen an allergy consultant so were able to educate him about nut allergy smile.

Have you kept a food diary, with full details of what your child has? Digestive symptoms can be allergy symptoms but are much more often intolerance - and a RAST test will not show an intolerance.

Yes her problems could be a stomach bug but stomach bugs can also cause problms digesting milk that can last for months afterwards. It's also possible to miss a trace of milk in something (bread?) and have problems recur if there is milk intolerance. And problems with wheat can make it appear that there are problems with milk but if you take wheat out of the diet then you can sometimes reintroduce dairy.

You probably would ahve to ask the paed about other tests, maybe a coeliac test. You need them to be eating wheat for a coeliac test to work but they don't have to be eating the food for a RAST to work.

Many problems like this are actually temporary and clear up in time anyway. Sometimes adding probiotics or digestive enzymes to the diet can help.

girlsyearapart that sounds more like allergy symptoms (especially the plum) so more point in having the tests, although it may be just be acids in the foods. Many babies projectile vomit, though.

wb Sun 21-Jun-09 20:07:55

Just wanted to add - at our allergy clinic they do RAST tests by pricking the end of the thumb and squeezing a few drops out (they wipe the thumb with something to stop the blood from coagulating for a few seconds) - very untraumatic.

DesperateHousewifeToo Sun 21-Jun-09 20:20:05

girlsyearapart - we were pretty clear that ds was allergic to egg and peanuts before being seen by specialist for testing.

He was about 3 1/2yrs at first test, I think, and had skin prick and RAST tests. He has had both (skin prick and rast) repeated yearly since then.

The initial tests clearly showed egg white and yolk allergy and peanut and hazlenut allergies.

The second year's test he was also tested for house dust, cats and dogs after an episode in a&e on a nebuliser.

Age 7yrs now. He has just been given the all-clear on egg allergy and is beginning to enjoy some new things in his dietgrin


NicknameAlreadyTaken Mon 22-Jun-09 11:52:07

tatt, yes, I tried keeping track of all she's eating and I was also tracking what I eat and at that time it helped me to detect what she was reacting to. She would react whenever I eat fruit, sugar, gluten, dairy and sweet vegetables till she was around 7-8 mo when she gradually got fine with me eating fruit, sugar and veg, then me eating gluten in a few months too, but kept reacting when I eat dairy. So, at that time, when I basically stopped eating a lot of stuff altogether to try and track her reaction, it was easy for me to keep my food diary but I can't really keep track of what I eat now as i'm only avoiding dairy (I always read the labels and try avoiding foods both for myself and for her where they say that it may contain traces of milk) and have loads of snacks during the day without having a spare minute to write it all down. smile Although I might try limiting my diet again to try and check if that makes any difference.

DD is not too fond of bread/cookies/cakes/etc, she occasionally eats a tiny bit of a sandwich though likes rye crisps and similar wheat ones. And she will often eat pasta.
So, it can possibly be wheat. Shall I try excluding wheat only to see if it helps? Or shall I exclude gluten containing foods (that includes wheat, rye, oats, etc)? I mean, is coeliac about wheat or is it about gluten?

When you say that tummy bug can cause problems digesting milk, do you mean any milk or do you mean dairy? (I'm asking because I still BF her quite a lot)

girlsyearapart, it does indeed depend on where you go. And I hope you find a good allergy dr for your DD!

And all in all, I feel a bit embarrassed to be making such a fuss out of my DD's digestive symptoms when there are a lot of babies and children with much severe problems sad
Hope they all get better!

tatt Tue 23-Jun-09 08:01:32

No-one likes their child being ill all the time, of course you want to make her better.

I wouldn't exclude gluten if your tests are due within 3 months, and I hope they are. You could try afterwards if the tests are inconclusive - and yes it would need to be all gluten. But I'd try probiotics or lactase first.

When someone gets a stomach bug it can kill off good bacteria in the gut. Some of those bacteria help digest lactose, which is in all milk including breast milk. However breast milk is more readily digested - forget why, can look it up later.

Have to dash off - but will come back

tatt Tue 23-Jun-09 10:10:29

Right back again - but have mega computer problems so not for long. Used to be thought that problems with lactose were all or nothing, now realised that most people tolerate some lactose but can be overloaded by large amounts. This would seem to fit with your child's symptoms as they build up. However problems with cows milk protein can present in a similar way as the protein gradually damamges the lining of the gut.

Basically its really difficult to work out if a child is intolerant to cows milk protein or lactose. Either way you'd probably just be told to avoid milk but it's useful to know because if it's lactose she can have low lactose milk and it won't make any difference if you have dairy in your diet. If its milk protein that is the problem milk in your diet will matter.

Although tests aren't very accurate you could ask about stool acidity tests (for lactose). Or you can buy lactase drops for her and see if they improve symptoms.

As it doesn't sound like allergy good news is she is likely to grow out of this anyway.

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