Food Allergies/anaphylaxis


what is the time frame for severe allergic reactions such as anaphylaxis to occur. I have read different answers to this on the internet. Some say within mins, while some say it can sometimes take up to a few hours or more. These are very varied times given. Thank you for any info.

Sorry about the delay in answering - password problems.

The time taken for anaphylaxis to occur depends on the type of exposure i.e. Whether injected intravenously, intramuscular or subcutaneous. With i.v. it's a matter of a few seconds to 1-2 minutes. Rather longer with intramuscular and longer still with s.c. But even with that, one would expect it to have started within 15 minutes.

With most foods, anaphylactic reactions can start with itching in the mouth within 1-2 minutes. Milk is an exception, because some of it's allergens can still be present in partial digestion products.

There are also rare cases of food-dependant exercise-induced reactions. Reactions come on if exercise follows a relevant meal anything up to 3 hours later.

If there are no positive skin prick tests to the suspected allergen, then the chances of anaphylaxis are effectively zero. Hope this helps. Get back if it does not.

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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Well, apart from the FRCP, I'm no longer active in the area.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!

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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.

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