Food Allergies/nut allergies


QUESTION: good evening,
how often should one be retested for allergies and are skin pricking allergy tests very accurate,or would another type of allergy test be more accurate. i had the skin pricking test 7yrs ago and was wondering if its still good, could one develope different allergies in that amount of time.

I just want to be sure if i was to eat a food that i havent in awhile or never have would do me any harm now if it was negative on the test i had seven yrs ago. I do not eat nuts like cashews, pecans, walnuts, or brazil nuts much and i am concerned i may be allergic now even tho i wasnt allergic to the nut mixture they used in the allergy test. i have only eat these maby a few times, and a couple i have never tried in my life so just worried to eat them now or to even be around them due to fear of a severe allergy.

My boyfriend had a nut mix tonight and was nervous to touch anything that he did after he ate them , so scared that i was going to have a reaction to some of them, now i do eat alot of peanuts and almonds-so i now im good there, but i buy them alone and not in any kind of nut mix.

If one was severly allergic (say anaphylaxis), to nuts or any other kind of food how long would it take to show up after it hits your mouth. I very concerned as you can tell about anaphylatic reactions. thank you , any advice is greatly appreciated.


Skin prick tests are the most useful of the several forms of allergy testing. They have a better correlation with clinical sensitivity. While one can have positive skin reactions and no clinical reaction on eating and vice versa. However, One can say that severe allergic reactions (like anaphylaxis) never occur in the absence of a negative skin test.

You did not mention your age. I assume you are young(ish). Levels of sensitivity do vary with time. In general, levels of sensitisation do tend to remain steady and fall gradually with age. However, some individuals get progressively more severe reactions with each exposure and these people are at significant chances of developing anaphylaxis.

Testing with true tree nuts needs to be done with each separate species of nut. Despite commonly held views, there is no clinical cross-reactivity between nut species. People who react to true nuts do have a greater than average reactivity to peanuts, but it is not universal.

Anaphylaxis is a very acute sudden drop in blood pressure after being exposed to something you have eaten or with which one has been injected. It usually comes on within minutes. The drop in blood pressure is so severe that it can cause unconsciousness, or even death. Itching and swelling in the mouth is a very common first sign. However, itching and/or swelling of the mouth does not often lead to fatality. Anaphylaxis is treated with adrenaline. It provenly prevents death if given within 5 minutes of the attack starting. This is why sufferers are usually given preloaded syringes of adrenaline for self injection. Just getting mouth symptoms alone is Not an indication for adrenaline.

Get back if this does bot answer your worries.

---------- FOLLOW-UP ----------

QUESTION: thank you doctor
when you said ;One can say that severe allergic reactions (like anaphylaxis) never occur in the absence of a negative skin test', sorry for being an idiot and asking but did you mean that if an allergy came back negative then that person would not have an anaphylatic reaction to that item.

So how valid is the nut mixture they used on me for testing be since you said they have to test with each seperate nut species, so those results they gave me as negative for nuts may not be all that accurate  and would i need more testing. and since my last allergy test was 7yrs ago, should one go back to be redone to see if any changes have taken place with those allergies (If new ones has popped up)

When someone that has eaten nuts of any kind touch something like a handle, door knob , etc, how long does the nut allergen residue stay active or stay there. (in the case someone did have an allergy to nuts and came in contact with that item). sorry for all the paranoid questions again, i do appreciate your insight and time.

ANSWER: Hi Jackie,

1. Yes. I do mean that if one has a negative skin prick test, the chances of suffering anaphylaxis after eating that nut are effectively zero.
2.Skin testing with a mixture of nuts is probably pretty meaningless as a diagnostic test. If one is positive, then I would consider it mandatory to test each species of nut separately. As I said before, there is no cross reactivity between nuts of different species (Proven by work in my own lab. You could have anaphylaxis to say walnuts and have no reaction at all to all the rest).
3. Whether new allergies "just pop-up" is very much dependant on your age. That's common in childhood, but becomes rarer after the 20's. It is more likely that old allergies will gradually become less severe and even go away. However just rarely new allergies can come on at any time. I once saw an old lady who first developed grass pollen hayfever at age 96!
4. The chances of you getting enough allergen from a doorknob are so low, it ought to be written up in the scientific literature.
5. I see more people whose lives are ruined by unreasonable fears about potential anaphylaxis than I do with people harmed by it. That is commonly doctor-induced by poor information transfer from doctors who do not know the subject. I've treated lots of patients who have had anaphylaxis. Being aware of the risks and prompt action have prevented death in every one.

But here's a question: Why are you so worried about nuts if you have never had a reaction? That you are seems a bit odd to me. Perhaps I have missed a crucial point?

---------- FOLLOW-UP ----------

QUESTION: thank you for getting back so quickly again,
to answer your question on why im so worried about nut allergies is because i have read sooo much about people that are being affected by nut allergies and i usually read or hear about those that get very severe reactions to them. I also have bad obsessive compulsive disorder, and deadly reactions , like anaphylaxis always worry me. I think 'oh thats going to get me someday' Its not just related to nuts but i worry about bad allergy reactions to medications as well, its a horrible time for my poor doctors to get me to take a new medication, i worry that im going to swell up, stop breathing and die whenever i have to take a new medication. I will sit for hours after taking a new med waiting for any allergy type symptom to kick in so i can rush to the ER. I became very nervous on bad allergic reactions to meds when i picked up an antibiotic and i asked the pharmacist whats the worst i may be looking at as far as reactions go and was told that if i was badly allergic to it i could have an anaphylatic reaction and not breath . I had never heard of anaphylaxis until that time and it stuck in my head ever since.  Its not a happy way to live unfortuantly but i have had this disorder for more than a decade (im now 35yr old) and take paxil to take the edge off. Sorry for the long story, i appreciated all your great information  ;)

Questions for you:

1. Have you yourself ever had atopic eczema, asthma, hay fever or other form of nose allergy?
2 If you have brothers or sisters and if so, did they or either of your parents have any of those?
3. Were any of your previous skin tests positive? That is, significantly larger than the positive control?
4. Did you have any blood tests. In particular, was serum IgE measured?

Food Allergies

All Answers

Answers by Expert:

Ask Experts


David Pearson


Any in the field I believe. Only experience of questions that get asked will tell.


I am a retired medical academic from the UK. I have done major research on Food Allergy and have been a government adviser in the area. 30 years experience running an allergy clinic. And undergraduate and post-graduate teaching.

Well, apart from the FRCP, I'm no longer active in the area. I'm too busy writing books. And I no longer have the cash to go to international meetings. But was active in many.

Will 120 scientific papers help? Chapters in books. Patient advisory materials. Magazine articles. TV appearances. Live and recorded. National and international invited lectures, etc. It was my job for 40 years. Do you think I count!

MD, PhD, Postgraduate Diplomas etc. Fellow of the Royal College of Physicians. etc. But I don't want that put out on the net! Just to let you know!

Awards and Honors

Past/Present Clients
Too many to count, patients of course and a large number of all sorts of corporate consultancies and considerable work as an expert witness in the Courts. I'm volunteering because your Greek expert has been so helpful, I thought I'd offer something back.

©2017 All rights reserved.