Allergy blood test

[SilverLining]

How beneficial are blood tests?
Are they usually ordered if scratch tests are positive, or negative?

My environmental scratch tests were all negative. Doctor recommended I get the blood test for cat, to be certain. (I think he said the blood test tests for something different?)

He also wanted me to get blood test for peanuts and sesame seeds. I will be seeing him in about a month to get results of this blood test and will discuss then.

But, even if they test negative I'm not going to feel safe eating those things. In other words, I'm not betting my life on a test. Would I be reasonable in wanting a food challenge if the tests are negative?

DH, who has witnessed most of my reactions is opposed to me doing this.

[Macabre]

I assume they'd do food challenges if the tests were negative.

It's not only reasonable, it's typical—at least in the US.

We've done both skin and blood tests for DS and myself historically. DS also had the component test for peanut, and if you have the option, I'd get that. It's so much more informative.

For me last year, I had skin tests and blood tests. When both came back negative, the doctor's office then scheduled food challenges for different days.

I feel no fear now eating bread anywhere, but I have trepidation with shrimp. I'll eat it when I'm in Minnesota but won't eat it traveling. 

And I don't want to cook it at home because it seems gross to me and also DS is allergic to shrimp.

Just testing negative, I would not start ingesting. I think an in office food challenge is important.

[Macabre]

I fixed some typos above.

[hezzier]

Most of the tree nuts have component testing also, not all yet, at least when DS had his last one done.  I personally think it's a good thing since they have been able to predict a person's allergic response based on which proteins they are allergic to for peanuts and tree nuts.

Here's a story in favor for the blood test...DD did not react to the venom that was injected under her skin for bees except for one spot got a little tingly/itchy, but no redness.  So the allergist really thought DD's response, which was mild but could absolutely been an allergic reaction, was to the pain of the sting, but ordered the blood test anyway to be sure.  She called us and said she was surprised but yes in fact DD was allergic to yellow jackets and wasps and needed to carry an epi.

[SilverLining]

Thanks for input.

[Mezzo]

DD1 had skin tests done once as a child, and since then the allergists have done blood tests on her for peanut and latex. They don't want to do a peanut skin test because that could be dangerous, and the blood test gives them a good level (which is HIGH).

[SilverLining]

DD1 had skin tests done once as a child, and since then the allergists have done blood tests on her for peanut and latex. They don't want to do a peanut skin test because that could be dangerous, and the blood test gives them a good level (which is HIGH).

Do you mean dangerous because it's equivalent to eating peanut?

[Mezzo]

Not equivalent exactly but it's still putting it in her skin when she's extremely allergic and reactive to it.

[YouKnowWho]

We have done both over the years to see trends.  DS2 has a tendency to not be reactive during SPT - we think half life of antihistamines and other issues have made it so even the histamine doesn't react. His peanut is always tiny and left me questioning if he was even allergic as he had never reacted. But the component test showed likelihood of gut anaphylaxis which made bathroom issues make sense.  I suspect his fish rxn's are similar as he always has increased bathroom activity during Lent while eating out. (We have changed protocols for eating out but it took us far too long to realize he was reacting and not the start of a stomach virus which at one one point was far too common in our household).

DS1 has always had off the charts total RAST and tests at a Class 5 or 6 for wheat, rye and barley.  Egg for the longest time was a low Class 3/high 2.  We challenged once at age 6 but failed, finally outgrew at 19.  Via SPT and RAST he tests positive for almost everything (previous allergist was on a fishing expedition thinking he was skinny and short statured because he was eating his allergens instead of recognizing the he comes from a family of tiny folks.  Current allergist was able to work through data and had us challenge peanuts and tree nuts and write off his other "positives" to corn, rice, oats, dairy and soy as negatives because he was eating with no issue.

On flip side DS2 has low total RAST, low scores for fish, peanuts and tree nuts but the panel test for peanuts showed high chance of gut anaphylaxis.

[becca]

Typically, I see and read that if there's a history of reaction, that is as valid, if not more so, than skin or blood testing.  Our allergist said it to me.  Like with Mezzo's dd, he had no reason to risk skin testing dd, which is an exposure, because she very clearly reacted to peanut.  If she were to test negative to a previous allergen, the next step would be a challenge.  Dd is now 25, and has not persued testing for potential outgrowth and challenges.  It's possible she's not allergic to almonds.