False (?) negative allergy skin test - what does it mean?
March 21, 2022 12:29 PM Subscribe
My son has what appears to be a pretty mild shellfish allergy (sometimes gets hives on his face after eating shellfish). He tested negative at the allergist last week (skin prick test) after the long spiel about how unusual false negatives are. I'm trying to figure out this means and what, if anything, I want to do next.
It felt really...weird? Anticlimactic? To get the whole long speech about how "there are often false positives for these tests but a false negative is very rare", see zero reaction to the skin pricks, then basically get a shrug and a "well maybe it's just mild for now but it'll probably get worse so definitely have him stop eating shellfish anyway." He prescribed a "just in case" epipen and offered that we could schedule in-office food challenges if we wanted.
At this point, what are my next steps? Does he just cut these foods out of his life indefinitely? Do I try doing food challenges to narrow down what exactly he can and can't eat? What's the point of that? Is there ever a point when an allergist will say "yes, this certain subset of food is safe" or will there always be a ton of caveats about how poorly we understand the immune system and allergies can change or develop at any age?
It seemed in the office like they were basically saying "well, this is something that can be very time-consuming if you want it to be, but ultimately you won't ever actually know anything more than you know right now or feel you're able to behave differently." Is that accurate? Is there any point to spending more time or effort trying to nail down food allergies that don't have oral immunotherapy as a possibility?
This is my first experience with food allergies and allergists in general and I just felt like I was missing something. We have a relative with a similar allergy and her rule is that she eats shellfish if it's very fresh and rarely has a reaction. I've seen her eat a half dozen oysters in a sitting but I've also seen her take medication after reacting to clams. I can't imagine that this is something we could ever narrow down in an allergist's office though. Not like we're going to bring in oysters on the half shell to the office - and even then, would we ever really feel safe about it?
I appreciate that the allergist didn't try to give me some false sense of security. But I left feeling more confused, if anything. How do I food allergies???
It felt really...weird? Anticlimactic? To get the whole long speech about how "there are often false positives for these tests but a false negative is very rare", see zero reaction to the skin pricks, then basically get a shrug and a "well maybe it's just mild for now but it'll probably get worse so definitely have him stop eating shellfish anyway." He prescribed a "just in case" epipen and offered that we could schedule in-office food challenges if we wanted.
At this point, what are my next steps? Does he just cut these foods out of his life indefinitely? Do I try doing food challenges to narrow down what exactly he can and can't eat? What's the point of that? Is there ever a point when an allergist will say "yes, this certain subset of food is safe" or will there always be a ton of caveats about how poorly we understand the immune system and allergies can change or develop at any age?
It seemed in the office like they were basically saying "well, this is something that can be very time-consuming if you want it to be, but ultimately you won't ever actually know anything more than you know right now or feel you're able to behave differently." Is that accurate? Is there any point to spending more time or effort trying to nail down food allergies that don't have oral immunotherapy as a possibility?
This is my first experience with food allergies and allergists in general and I just felt like I was missing something. We have a relative with a similar allergy and her rule is that she eats shellfish if it's very fresh and rarely has a reaction. I've seen her eat a half dozen oysters in a sitting but I've also seen her take medication after reacting to clams. I can't imagine that this is something we could ever narrow down in an allergist's office though. Not like we're going to bring in oysters on the half shell to the office - and even then, would we ever really feel safe about it?
I appreciate that the allergist didn't try to give me some false sense of security. But I left feeling more confused, if anything. How do I food allergies???
My food allergies are cross reactive with my pollen allergies, so I have worse reactions on high pollen days. That said, why get more information about doing a food challenge in the office? It might bring peace of mind to know more clearly what to avoid.
posted by chocotaco at 1:05 PM on March 21, 2022 [4 favorites]
posted by chocotaco at 1:05 PM on March 21, 2022 [4 favorites]
Yes, my kid did the allergy test when young and it came back with nothing, and since then she's actually been to the ER for an allergy event that I guess was related to a virus...the ER wasn't really sure but they just wrote a prescription for an epipen and she's had one since with zero issues. That was 3 years ago (I think). Sudden allergic attacks can be weird.
posted by The_Vegetables at 1:17 PM on March 21, 2022
posted by The_Vegetables at 1:17 PM on March 21, 2022
Like, maybe one time when he got hives, the cook used Old Bay, but another time when he didn't, the cook just used salt and pepper or something. (This is an analogy I have pulled out of my ass.)
Maybe the Empress pulled this out of her ass, but it is exactly my experience. I was allergic to MSG, which is extremely rare, regardless of what people claim. As a consequence, I could have sausage one day and be fine, and the next day and break out in hives, or worse, have an astma attack, because the first sausage was made without MSG and the next was with it.
So maybe look for other aspects of the seafood servings. Old Bay could be the culprit! Or lemons.
The good thing is, after abstaining from everything with MSG for a couple of decades, I've almost grown out of it. I mean, if I ate a bag of twizzlers, or a jar of marmite, I would probably get sick. But I can eat something with soy in it, and parmesan cheese.
posted by mumimor at 2:18 PM on March 21, 2022
Maybe the Empress pulled this out of her ass, but it is exactly my experience. I was allergic to MSG, which is extremely rare, regardless of what people claim. As a consequence, I could have sausage one day and be fine, and the next day and break out in hives, or worse, have an astma attack, because the first sausage was made without MSG and the next was with it.
So maybe look for other aspects of the seafood servings. Old Bay could be the culprit! Or lemons.
The good thing is, after abstaining from everything with MSG for a couple of decades, I've almost grown out of it. I mean, if I ate a bag of twizzlers, or a jar of marmite, I would probably get sick. But I can eat something with soy in it, and parmesan cheese.
posted by mumimor at 2:18 PM on March 21, 2022
As a few others have mentioned, allergies are sometimes illogical and present weirdly. I would fill the prescription for the EpiPen and keep one in his school bag and one in your purse. Sometimes an allergy can flare up with a much stronger reaction than you'd previously seen.
If your son ever has trouble breathing or feels confused/lightheaded after a meal, inject him and take him to the ER. I have seen a lot of people come much closer to catastrophe than they'd intended by assuming that the level of allergic reaction they'd seen before is the one they'll see the next time.
posted by kate blank at 2:59 PM on March 21, 2022 [2 favorites]
If your son ever has trouble breathing or feels confused/lightheaded after a meal, inject him and take him to the ER. I have seen a lot of people come much closer to catastrophe than they'd intended by assuming that the level of allergic reaction they'd seen before is the one they'll see the next time.
posted by kate blank at 2:59 PM on March 21, 2022 [2 favorites]
Anecdata: I had a relative that could eat 7 large shrimp and be fine, but the 8th would make her react badly. And it was that specific and repeatable.
Seconding Empress. It's something you just need to figure out over time and space. And keep some Benedryl handy. It's cheap and readily available.
posted by JoeZydeco at 4:44 PM on March 21, 2022
Seconding Empress. It's something you just need to figure out over time and space. And keep some Benedryl handy. It's cheap and readily available.
posted by JoeZydeco at 4:44 PM on March 21, 2022
My mom has a mild shellfish allergy which also manifests as hives and which only gets triggered if 1) she eats more than 3 blue crabs or 2) the shellfish is below a certain level of freshness. I seem to be developing a similar reaction in adulthood (after a youth and early adulthood with absolutely no food allergies), and it seems to follow the same rules about volume and freshness. The reactions also seem more likely with crustaceans than bivalves.
Obviously I'm not telling you to gamble with your child's health or safety, but as a point of anecdata my mom's reactions never go past hives (and she likes shellfish enough to deal with the occasional reaction).
posted by Fish, fish, are you doing your duty? at 5:39 PM on March 21, 2022
Obviously I'm not telling you to gamble with your child's health or safety, but as a point of anecdata my mom's reactions never go past hives (and she likes shellfish enough to deal with the occasional reaction).
posted by Fish, fish, are you doing your duty? at 5:39 PM on March 21, 2022
Is it possible they have a food intolerance rather than an allergy? I did allergy testing after my face and tongue started randomly swelling up. Turned out the only allergy I have is a mild grass allergy, but through an elimination diet (supervised by an allergist and dietician) discovered that I have an intolerance to salicylates, which triggers after a build up of chemicals, so while something may be fine one day, it can trigger the swelling the next if I've had too many high salicylate foods. Note, the elimination diet is tough. You really need a dietician supervising due to the number of restrictions to make sure you still eat a reasonably balanced diet even when you can only eat one type of fruit and maybe 5 types of vegetables.
posted by Kris10_b at 7:04 PM on March 21, 2022
posted by Kris10_b at 7:04 PM on March 21, 2022
Allergies are weird and messy and even the experts don't have a complete understanding of them.
My son has several food allergies and each one is unique.
Eg. Sesame is easy. He had a very obvious reaction from eating it, and his test was positive. So we know to strictly avoid.
Wheat is more complicated because he can eat a couple of very processed foods which contain wheat, but reacts to most other wheat. Since he has a long list of other allergies, I don't want to limit his diet even more than necessary so with support of his allergist, we are keeping those couple of foods in his diet regularly and avoiding any new wheat for now.
Diagnosis of food allergies is an inexact science. Neither blood nor skin testing is perfect, at this time the most widespread reliable test is whether a person can eat the food without reacting. But even that is not always clear cut. Some children will get skin irritation, even including hives, but be able to eat the food.
Shellfish is a big umbrella, with two little umbrellas underneath for mollusks and crustaceans. I believe most shellfish allergies are to crustaceans. A person might react to one specific shellfish but not others. Eg. Might react to shrimp but be okay with crab. Another person might react to multiple or all.
What are your goals?
You could err on the side of extreme caution and practice avoidance, but that might limit the diet unnecessarily. Food challenges could open up some options and also allow you to know where you stand.
There are treatment options available (OIT or SLIT) but confirmation of a true allergy would be recommended before pursuing.
Good luck! Feel free to send me a memail if I can help further.
posted by kinddieserzeit at 12:39 AM on March 22, 2022
My son has several food allergies and each one is unique.
Eg. Sesame is easy. He had a very obvious reaction from eating it, and his test was positive. So we know to strictly avoid.
Wheat is more complicated because he can eat a couple of very processed foods which contain wheat, but reacts to most other wheat. Since he has a long list of other allergies, I don't want to limit his diet even more than necessary so with support of his allergist, we are keeping those couple of foods in his diet regularly and avoiding any new wheat for now.
Diagnosis of food allergies is an inexact science. Neither blood nor skin testing is perfect, at this time the most widespread reliable test is whether a person can eat the food without reacting. But even that is not always clear cut. Some children will get skin irritation, even including hives, but be able to eat the food.
Shellfish is a big umbrella, with two little umbrellas underneath for mollusks and crustaceans. I believe most shellfish allergies are to crustaceans. A person might react to one specific shellfish but not others. Eg. Might react to shrimp but be okay with crab. Another person might react to multiple or all.
What are your goals?
You could err on the side of extreme caution and practice avoidance, but that might limit the diet unnecessarily. Food challenges could open up some options and also allow you to know where you stand.
There are treatment options available (OIT or SLIT) but confirmation of a true allergy would be recommended before pursuing.
Good luck! Feel free to send me a memail if I can help further.
posted by kinddieserzeit at 12:39 AM on March 22, 2022
I just wanted to add that if your child has a true allergy, it can be risky to think of it as "mild" even if reactions so far have been mild. Reactions can be unpredictable and there have been multiple deaths because people underestimated how serious their reaction could be.
posted by kinddieserzeit at 12:51 AM on March 22, 2022 [2 favorites]
posted by kinddieserzeit at 12:51 AM on March 22, 2022 [2 favorites]
I went into anaphylactic shock in college after eating a honey roasted peanut. Never had an issue before, completely out of nowhere. I had an allergy panel after to confirm and was negative to peanut allergy. No issues with peanuts since.
Turns out that I do have an extreme mold allergy and my best guess is that it was present at the processor or on the nuts.
posted by coldbabyshrimp at 6:52 AM on March 22, 2022 [1 favorite]
Turns out that I do have an extreme mold allergy and my best guess is that it was present at the processor or on the nuts.
posted by coldbabyshrimp at 6:52 AM on March 22, 2022 [1 favorite]
Coming back in to add another "allergies can be really weird" anecdote:
I've always had occasional mild seasonal allergies. They were low-level enough when I was a kid that I just lived with it - just sniffles and sneezes in the morning once in a while that usually went away in a few hours and that was that. I'd just sneeze some, blow my nose a few times and go about my business. Then when I was 25, I went to visit New Orleans for the first time - I was there in summer and had stronger seasonal allergies one morning. I was in a youth hostel and sharing the room with a Med Student at Tulane - and when I wondered aloud why my allergies were so bad when usually they weren't, she told me that "Oh, we're below sea level, so that probably is making for a greater concentration of whatever it is that you're allergic to, and that's why you're fine at home but you're reacting here."
Made sense to me. And as I got older, I started paying attention more, and started trying to figure out just what is it that causes them. And after about 15-20 years, the only consistent factor I've found is: weather. There is a very narrow temperature range and a very specific humidity level, where if we hit it, I am prone to getting seasonal allergies.
I can only assume that there's some kind of mold or spore or fungus or something that only does its thing when it's between 50-65 degrees and we are at 60% humidity (or whatever it is), and that that thing is my trigger. But it's still so mild I have given up trying to figure it out - I still only get stuffiness and sometimes itchy eyes - and I've learned to just have some Flonase in the medicine cabinet so I can hit myself up when I wake up with either one of those. And that's seemed to take care of things, so I go with what works and leave it at that.
posted by EmpressCallipygos at 8:02 AM on March 22, 2022
I've always had occasional mild seasonal allergies. They were low-level enough when I was a kid that I just lived with it - just sniffles and sneezes in the morning once in a while that usually went away in a few hours and that was that. I'd just sneeze some, blow my nose a few times and go about my business. Then when I was 25, I went to visit New Orleans for the first time - I was there in summer and had stronger seasonal allergies one morning. I was in a youth hostel and sharing the room with a Med Student at Tulane - and when I wondered aloud why my allergies were so bad when usually they weren't, she told me that "Oh, we're below sea level, so that probably is making for a greater concentration of whatever it is that you're allergic to, and that's why you're fine at home but you're reacting here."
Made sense to me. And as I got older, I started paying attention more, and started trying to figure out just what is it that causes them. And after about 15-20 years, the only consistent factor I've found is: weather. There is a very narrow temperature range and a very specific humidity level, where if we hit it, I am prone to getting seasonal allergies.
I can only assume that there's some kind of mold or spore or fungus or something that only does its thing when it's between 50-65 degrees and we are at 60% humidity (or whatever it is), and that that thing is my trigger. But it's still so mild I have given up trying to figure it out - I still only get stuffiness and sometimes itchy eyes - and I've learned to just have some Flonase in the medicine cabinet so I can hit myself up when I wake up with either one of those. And that's seemed to take care of things, so I go with what works and leave it at that.
posted by EmpressCallipygos at 8:02 AM on March 22, 2022
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You've said, though, that your son somtimes gets hives when eating shellfish - which has me wondering if it's the shellfish itself, or something that maybe was cooked with the shellfish but that wasn't other times when your son didn't have a reaction. Like, maybe one time when he got hives, the cook used Old Bay, but another time when he didn't, the cook just used salt and pepper or something. (This is an analogy I have pulled out of my ass.)
And you could try to figure it out if you wanted - or you could just avoid shellfish to play it safe if you wanted. I don't eat shellfish all that often myself, but for different reasons (I grew up in New England where we caught our own, and I am THOROUGLY spoiled now and since I can't get it that fresh I don't eat it), and still have a well-rounded and satisfiying diet. If you or your son are uneasy about the whole seafood thing you could just avoid it.
Or, if you want to just wait and see what happens - if he has another reaction, you've got the epi-pen to help if it gets serious. But also try to find out exactly what possible triggers were there in every detail - like, what were the exact ingredients, what kind of shellfish, when was it caught, and so on. If you can, even check what detergent was used to wash the napkin he wiped his mouth with. And then save that, and if he gets another reaction to a different meal, write down all those details too. And over time you may start to notice a pattern ("oh, hang on, this only happens when we eat clams that were dug up from the beach near the old steel smelting plant!" or whatever).
posted by EmpressCallipygos at 12:53 PM on March 21, 2022 [5 favorites]