The description seems consistent with anaphylaxis related to dog protein, with salivary contact, possible ingestion, inhalational exposure as reflected in the rhinitis and exposure via the skin with the atopic dermatitis. All of these allergen contacts potentially provided a sufficient dose to result in severe, systemic symptoms. I am surprised the specific-IgE for dog is not greater, but the severity of symptoms do not correlate with the specific-IgE value and the quantity of specific-IgE may increase if tested later. I feel the decision to remove the dog from the family was a wise one. An inadvertent food ingestion is always a concern as is delayed, mammalian meat anaphylaxis due to galactose-alpha-galactose sensitivity, but I think you have addressed these concerns.
I have attached a question from the Ask The Expert Archives. Dr. Lieberman, who has an extensive clinical experience with anaphylaxis, acknowledges that animal contact can result in anaphylaxis. I also could not find a case report to support, but I certainly have seen dramatic skin symptoms with animal contact, indicating allergen can penetrate a keratinized surface. Atopic dermatitis would increase this possibility. Dust mite allergen absorption through the skin has been suggested (Jang). Peanut sensitivity through environmental exposure and skin contact has also been suggested (Brough).
I would discourage an indoor mammalian pet and provide epinephrine autoinjectors until you are more confident the episode was dog related. As Dr. Lieberman mentions, up to 50% of anaphylaxis episodes are idiopathic.
Jang, Y. H., et al. "House dust mite allergen induces atopic dermatitis via Toll-like receptors 1 and 6 triggering of keratinocytes." British Journal of Dermatology. Vol. 170. No. 6. 111 River ST, Hoboken 07030-5774, NJ USA: Wiley-Blackwell, 2014.
Brough, Helen A., et al. "Atopic dermatitis increases the effect of exposure to peanut antigen in dust on peanut sensitization and likely peanut allergy." Journal of Allergy and Clinical Immunology (2014).
Anaphylaxis: Reaction to banana versus exposure to dog
17 year old boy had anaphylaxis on 1/16, onset 4 PM. He was with a dog for 15 minutes about 30 minutes prior to onset of anaphylaxis. He ate a banana about 15-30 minutes prior to onset of anaphylaxis. Reaction described as hives, tight chest, cough, dizziness. In ED he had hives, uvula edema. EMS was called and he was treated with epi, albuterol. In the ED he got IV steroids, epi, albuterol. He initially improved but hives returned and he was admitted for management. Sent home on prednisone, benadyrl, albuterol, flovent and given an epi pen He was told to avoid pets and banana. He has eaten bananas, in the past, a few times a week without problem. He had eaten a banana at 11 AM on 1/16. He sometimes has a stuffy nose, wheeze on exposure to some dogs, but other dogs do not trigger any reaction. He has asthma, onset age 3 years old. No admissions. He now has symptoms once a year on exposure to some dogs, horses. Uses albuterol.
Patient states in ED he was told maybe he reacted to pesticides in the second banana he ate on 1/16
IgE dog greater than 100 kU/L
IgE Banana less than 0.35 kU/l
Given the frequency with which he has eaten bananas in the past it does not seem likely that this is trigger. Can you see negative allergy test for a food soon after a major reaction to the food? Could he have reacted to pesticides in the food? I thought he should get skin tested with fresh banana and then have a challenge to banana. Can this be done now or should he wait a while?
I know the IgE to dog is very high. Given the past history of tolerance to some dogs as well as infrequent reaction to other dogs, does the present history of anaphylaxis fit with a reaction to dog?
Also, can one sometimes see a negative IgE test to an aeroallergen trigger soon after a severe reaction to it?
First, it should be remembered that you may never find the cause of anaphylaxis in this young man since in this age group, perhaps as many as 50 percent of episodes are idiopathic in nature (1).
Secondly, you did not mention pertinent negatives such as whether or not he took any medication (e.g., a nonsteroidal agent, et cetera) prior to the reaction. I feel certain that you have asked this question, but for completeness sake, I wanted to mention it.
Having said this, I will try and answer each specific question, but as you know, there may not be any definitive answer to these issues.
Yes, you can certainly have a false-negative "allergy test" to a food, which when ingested, can produce anaphylaxis. This can be true for both skin tests and in vitro tests. I am unaware of any study that has looked at whether this is more common immediately after a reaction than it is, for example, a month or so later. However, on rare occasions, such tests can be false-negative. As you know, based upon the planned strategy to deal with this patient, they are more likely to be false-negative to commercial tests than to a "prick to prick" test using fresh food.
I really believe that it would be highly unlikely that this reaction was to a pesticide in the food. I doubt that this is an issue worth pursuing.
There is no "set time" after a reaction at which an oral challenge test can be performed. I feel that a wait of two weeks would be reasonable.
There have been very rare reports of anaphylactic reactions to inhalants. Certainly, wheeze and contact urticaria are not infrequently encountered when patients allergic to an animal have physical contact with that animal. It is possible therefore that the reaction was due to exposure to dog, but in view of the prolonged nature of the event with recurrence after treatment, it is unlikely that the dog was the culprit. Nonetheless, I do not think that we can rule this out.
I am not completely sure regarding the meaning of your question about the "negative IgE test." Are you speaking of a skin test or a serum-specific IgE? If it is a skin test, theoretically, a positive test could convert to negative after an anaphylactic event (this is one reason why we delay skin testing to hymenoptera until two weeks after the episode). I assume that this could be true for a skin test to an aeroallergen as well. As far as a serologic test, I do not think we have an answer for you. We assume that the most likely reason the skin test might be negative is that mast cells take time to regenerate mediators, and the test could be false-negative because of depletion of these mediators.
Theoretically, a serum-specific IgE test, if antigen was bound to IgE at the time the test was done, could become negative as well. However, I am not aware of any studies that have looked at this issue, and therefore cannot give you a trustworthy answer. But in more than likely a serologic test should be positive irrespective of the time it is performed.
Having said this, I think your planned strategy to approach the problem is on target.
Also, we would greatly appreciate any follow-up, especially if you do determine the cause was the banana. Thank you again for your inquiry and we hope this response is helpful to you.
1. Webb L, Green E, and Lieberman P. Anaphylaxis: A Review of 593 Cases. Journal of Allergy and Clinical Immunology, Volume 113(2):S240 February 2004.
Phil Lieberman, M.D.
I hope this information is of help to you and your patient.
All my best.
Dennis K. Ledford, MD, FAAAAI