Category Archives: Allergy

Preventing Peanut Allergy: The LEAP Trial


I am delighted to announce that my review of the LEAP trial, which was published this spring in the New England Journal of Medicine, is now live at  Here is the long hyperlink:  This very exciting trial is a landmark.  I hope that you enjoy my review and share it with interested people.

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Cannabis Allergy: It’s Real!



People tend to wink at me when I say I have been to Grateful Dead concerts but never smoked marijuana.  Then I get looks of incredulity when I share that, aside from enjoying the excellent music, I really suffered from allergy symptoms during these concerts.  I would sneeze uncontrollably, my eyes would itch and water, my nose would run, and the roof of my mouth would itch.  Well, Doubters, now there is a nice review manuscript about cannabis allergy.  Yes, its real!

Here are some fun facts:

  • Cannabis sativa is a flowering plant that releases pollen in the late summer to early  autumn. The pollen grains are very buoyant, which can lead to distribution across many miles.  Wild growth does occur and Cannabis pollen is relevant in central India, urban Pakistan, southern Europe, and parts of the United States.  This Blog has had readers from all of these parts of the world.
  • The primary psychoactive component of Cannabis, delta-9-tetrahydrocannabinol (THC) may be an allergen as well.  This is especially important because, in the cultivation of Cannabis, efforts are made to increase amount of THC in the plant.  Some strains of Cannabis contain as much as 22.6% THC.
  • Regular smokers of Cannabis have reported wheezing, sputum production, and chronic cough.  However, studies have also shown that marijuana smoking can lead to acute bronchodilation and even reversal of methacholine- and exercise-induced bronchospasm. Parenthetically, this reminds me of that Peter Tosh song “Legalize It,” in which the Reggae master extolled the many perceived virtues of marijuana.  One of these was “it’s good for asthma.”  For decades I thought this lyric was just silly.  It is interesting, now, to read that marijuana smoking can temporarily relieve some aspects of asthma.
  • In people who have Cannabis allergy, marijuana smoking can trigger asthma, with symptoms such as wheeze, cough, and chest tightness.  I’m sorry, hopeful readers, but medical marijuana is not going to be indicated for the treatment of asthma.
  • Along with asthma, the inhalation of Cannabis pollen can cause other symptoms typical of allergy to a plant pollen, including runny nose, sneezing, itchy nose, watery eyes, itchy eyes, and an itchy throat.
  • Skin contact with Cannabis plant material has been associated with hives, generalized itching, and swelling around the eyes.
  • Anaphylaxis (a life-threatening allergic reaction), with such symptoms as hives, swelling, difficulty breathing, and difficulty speaking has been associated with eating hemp seeds (which come from the Cannabis plant).
  • Occupational allergy in several forms has also been described with exposure to Cannabis. One such report involved two patients who were workers in a forensics laboratory and were non-users of Cannabis.  They reported nasal and respiratory symptoms after working with marijuana and hashish (both, of course, made from the Cannabis plant).  One of these patients had more severe symptoms when handling material with especially high THC. There is also a separate report of an employee of a forensic laboratory who developed hives after handling marijuana.
  • Some people with allergy to Cannabis have also been shown to have cross-reactivity with foods, including tomato, apple, almond, eggplant, chestnut, pepper, fig, peach, banana, and citrus, with symptoms such as hives, sneezing, and, even, anaphylaxis.

This brief summary of allergy to Cannabis shows that people can be sensitive to different manners of exposure (inhaled, contact, and ingestion) to different parts of the plant (pollen and leaves).  While this allergy does not appear to be common, it is important to be aware of the possibility of Cannabis as a source of sensitivity as it is increasingly accepted in society.

Published March 7, 2015


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Ocampo TL and Rans TS, Cannabis sativa: the unconventional “weed” allergen. Ann Allergy Asthma Immunol 2015 Mar;114:187-192.


Does Exercise Cause Allergy?



Today’s article takes the concepts forward that were discussed in the first post on this blog (only 6 weeks ago: “Does Exercise Lead To Colds?”) with consideration of allergy as a cause of cold-like symptoms (upper respiratory tract symptoms, URS).  The idea for the previous article about exercise and colds (upper respiratory infections) had to do with the commonly-held impression, among athletes, coaches, and physicians, that athletes weaken their immune systems during peak training and races and, therefore, make themselves sick.  The evidence, however, does not support this idea.  Instead, it appears that URS may be a function of the release of inflammatory mediators and not, necessarily, infection.  Now, there is growing evidence that much of these URS associated with exercise may, actually, represent respiratory allergic disease.  Since respiratory allergic disease can be tested and treated, this concept has important implications for training and performance.

For researchers to begin to approach the question of the relationship between exercise and allergy, they first need a good tool to measure the incidence of allergy in athletes  Such a tool, the self-reported Allergy Questionnaire for Athletes (AQUA), was developed and validated, by Bonnini et al, in 2009.  The study group was professional soccer players (football for the rest of the world outside of the U.S.).  Skin testing for allergy (which is a gold standard) was positive for 46.8% of these athletes.  An AQUA score of 5 or higher gave a specificity for allergy of 97.1% (meaning that, for athletes with a score of 5 or higher, there is a 97.1% chance that they have allergy) and a sensitivity of 58.3% (meaning that this score only identifies 58.3% of athletes with allergy or, to put it another way, nearly 42% of athletes with allergy can be missed with a cutoff AQUA score of 5 or higher).  In other words, an AQUA score of 5 or higher almost always indicates allergy, but the rate of allergy can be under-reported.  The AQUA has been used for a number of studies since it was developed and validated.

Once such study was of 201 Brazilian elite marathon runners.  To be included in this study, athletes, between age 20 and 50, had to have completed, in the prior 18 months, a marathon in under 2:35 (men) or 3:00 (women) or a half-marathon in under 1:23 (men) or 1:35 (women). Since elite runners train outdoors for extended periods of time with a high ventilatory rate, this is an ideal group in which to consider the relationship between exercise and allergy.  This study found that 60% of these elite runners had allergy, as defined by an AQUA score of at least 5. There were no significant differences between the AQUA negative and the AQUA positive groups in gender, age, running experience, weekly training volume, and best performance time. This finding of 60% (which may be under-estimated, as explained, above) is higher than the estimated rate of allergy in the general population (which is roughly 10-30% of adults).

In “average” marathoners, allergic respiratory disease is also important.  For example, 208 participants in the 2010 London Marathon were enrolled in a recently-published study.  The average age of participants was 40.3 years for males and 37.4 years for females.  On average, participants trained 7.6 hours per week for the race and the average finishing time was 5.1 hours.  It was found that 40% of runners in this study had allergy as defined by a positive AQUA questionnaire plus objective evidence of sensitization (allergy identified with a screen of blood samples for specific IgE, which is the “allergy antibody”).  This is higher than the rate of allergy for the general population.  The researchers also found that 47% of the runners experienced URS after the marathon, but only 19% of non-runners residing in the same households as study participants experienced URS.  Furthermore, a positive AQUA was a significant predictor of URS after the race.  Therefore, endurance running was associated with the development of URS and allergic respiratory disease was also associated with URS.

Aside from increased exposure to environmental allergens and increased rate of respiration with extended outdoor exercise, there is evidence that strenuous or excessive exercise can predispose individuals to a TH2 cytokine profile (this is found in people who have allergy).  In other words, strenuous or excessive exercise can “unbalance” athlete’s immune systems toward allergy.  Furthermore, one of the cytokines that has been shown to be increased after strenuous exercise (running, in fact) is IL-6.  Please recall the post “Does Exercise Lead To Colds,” in which it was discussed that IL-6 is elevated in athletes with URS.

Therefore, it appears that the rate of respiratory allergy is higher for both elite and non-elite runners.  Furthermore, there is a known mechanism that can explain this increased rate of allergy.  In the study of London Marathon participants, more than half of these athletes felt that they had allergic disease.  However, of this number, 77% were not using any form of medication, a quarter of whom did not do so for fear of affecting performance.  This fear is unfounded.  In fact, respiratory allergic disease can have negative effects upon exercise performance.   Therefore, for endurance athletes with upper respiratory symptoms associated with training and racing, it is worthwhile to be evaluated for allergy.  In the United States, Board-certified allergist/immunologists can be found at ACAAI and AAAAI.  But there are professional allergist’s societies around the world from whom an athlete can find help.

 Published February 17, 2015


Bonini M, Braido F, Baiardini I, et al. AQUA: Allergy Questionnaire for Athletes.  Development and validation. Med Sci Sports Exerc. 2009 May;41(5):1034-1041.

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 Komarow HD and Postolache TT. Seasonal allergy and seasonal decrements in athletic performance. Clin Sports Med. 2005 Apr;24(2):e35-e50.

 Robson-Ansley P, Howatson G, Tallent J, et al. Prevalence of allergy and upper respiratory tract symptoms in runners of the London marathon. Med Sci Sports Exerc. 2012 Jun;44(6):999-1004.

 Smith LL. Overtraining, excessive exercise, and altered immunity: is this a T helper-1 versus T helper-2 lymphocyte response? Sports Med. 2003;33(5):347-364.

 Steensberg A, Toft AD, Bruunsgaard H, et al. Strenuous exercise decreases the percentage of type 1 T cells in the circulation. J Appl Physiol. 2001;91(4):1708-1712.

 Teixeira RN, Mendes FAR, Martins MA, et al. AQUA as predictor of allergy in elite marathon runners. World Allergy Organ J. 2014;7(1):7