First Case of Allergy to Secondhand Marijuana Reported

Marcia Frellick

November 20, 2018

SEATTLE — A 6-year-old boy with severe asthma who was not responding to treatment was found to have an allergy to the marijuana being used in his home in what researchers describe as a first-of-its-kind case.

Although allergy to marijuana has been reported in adults who use it, this is the first report of a young child with a positive allergy test who was exposed only to secondhand smoke, said Bryce Hoffman, MD, from the National Jewish Hospital in Denver.

"Nothing was helping the boy get better," Hoffman said here at the American College of Allergy, Asthma & Immunology (ACAAI) 2018 Annual Scientific Meeting. "He was having almost daily symptoms of cough, shortness of breath, wheezing. Then we found out that some family members had recently started smoking marijuana in the house."

Family members said they weren't using the drug in the same room as the child, but the information was enough to test for allergy, Hoffman said. In addition, the child's grandmother said she had broken out in full-body hives when she had used marijuana in the past.

Researchers added saline to the same kind of cannabis the family had been using to create a puddle sample and pricked the skin of the patient with it. They also pricked the skin of his grandmother and a negative control subject.

The wheal diameter of the patient was 9 × 8 mm and of the grandmother was 15 × 8 mm. The control subject tested negative.

Results from additional tests were compared with those from the control subject, including a basophil activation test of cannabis, as well as peach and tomato, which have been shown in the literature to have a cross reaction to cannabis, Hoffman said.

He was having almost daily symptoms of cough, shortness of breath, wheezing.

"The patient demonstrated basophil activation to cannabis with pronounced differences compared to the control at the 1:20 and 1:100 dilutions," the researchers write in their poster. The peach and tomato tests were negative.

"We felt this was pretty good evidence that this patient was allergic to cannabis," Hoffman said.

The team asked the family to rid the house of any marijuana to further test the findings and, 3 months later, the boy's "symptoms were all improved."

Before the marijuana was removed, the boy had a score of 19 on an asthma-control questionnaire.

Three months after the marijuana smoke was removed from the house, his score was 25. Importantly, his average impulse oscillometry R5-R20 score went from 2.35 to 1.37 — 1.50 is abnormal, Hoffman noted — showing improvement in peripheral airway disease.

"He got better objectively and subjectively," he said.

This finding suggests a line of questioning for physicians about family marijuana use that might not come to mind when the hard-to-control patient is a young child, especially as more states legalize the drug for medical and recreational use, Hoffman told Medscape Medical News.

Ask About Marijuana Use in the Home

Although many allergists ask about cigarette smoke in the house, questions about marijuana are not often asked, he said, especially with young patients.

It is unclear whether the marijuana smoke itself or traces on furniture or clothes, for example, are the problem. That should be part of further study, he said.

"We also need to find better ways to test it," he said, noting that using the whole plant has limitations because it has several components.

"We all know marijuana smoke is an irritant. The big news on this is that there are people who are actually allergic to it. They have a positive allergy test. It's not just an irritation," said ACAAI President-Elect Allen Meadows, MD, from the Alabama Asthma and Allergy Clinic in Montgomery.

An immune reaction will amplify a very small exposure, whereas with an irritant like tobacco smoke, small exposure means small symptoms. "I think it had always been assumed that it was the same for marijuana smoke," Meadows told Medscape Medical News.

Although the findings are based on a single case, the conclusions say, "wow, we should look at this," he said.

Hoffman and Meadows have disclosed no relevant financial relationships.

American College of Allergy, Asthma & Immunology (ACAAI) 2018 Annual Scientific Meeting: Abstract M076. Presented November 16, 2018.

Follow Medscape on Twitter @Medscape and Marcia Frellick @mfrellick



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