Image of male marijuana plant leaves

With the legal status of marijuana changing in a growing number of states, allergists expect to see more patients who experience allergic reactions to the pollen-bearing plant also known as cannabis.

Smoking marijuana for either medical or recreational use or inhaling its smoke could cause a flare-up of asthma symptoms, allergic rhinitis or conjunctivitis, according to a research paper published in the March 2015 issue of Annals of Allergy, Asthma and Immunology.

Allergy symptoms include nasal congestion, eye inflammation and coughing, wheezing and sneezing. Skin contact with marijuana – including the hemp version sometimes used in clothing – may cause eczema or hives.

And there is one reported case of a man who experienced anaphylaxis after consuming hemp seed-encrusted seafood. Anaphylaxis is a severe, potentially life-threatening allergic reaction.

As an airborne allergen, cannabis pollen grains typically emerge in late summer or early autumn. They are “very buoyant, allowing for distribution across many miles,” the researchers say.

Another allergen associated with marijuana? Mold. Representing Allergy & Asthma Network, Purvi Parikh, MD, a pediatric allergist and immunologist in New York City, told the website that marijuana plants can become very moldy in storage.

Marijuana allergy cases remain uncommon – for now. It’s likely they have been around for years but went unreported due to marijuana’s illegal status, Dr. Parikh says.

In recent years, Colorado, Washington, Oregon, Alaska and the District of Columbia legalized marijuana for recreational use. It was already legal for medical purposes in 23 states.

Dr. Parikh expects to see more cases of marijuana allergy in the years ahead. “It is going to become increasingly more common,” she says.

Is there treatment?

People who suspect they are allergic to marijuana – whether it’s the pollen in the cannabis plant, mold from storage, or something else – should talk with a board-certified allergist.

The best treatment is avoidance. Certainly people with asthma who count cigarette smoke as a symptom trigger should similarly avoid marijuana smoke.

Prescription and over-the-counter asthma and allergy medications can help prevent and treat symptoms that arise from being around marijuana. These may include albuterol inhalers and inhaled corticosteroids for asthma and antihistamines, intranasal corticosteroids and nasal decongestants for allergies.

Epinephrine auto-injectors should be used as the first line of treatment for anaphylaxis.

Houston allergist and immunologist Ashwini Reddy, MD, representing Allergy & Asthma Network in a recent Fox 26 Houston television interview, noted that allergic reactions to marijuana could develop and worsen over time. “It may not happen the first time you’re exposed to it,” she says.

Currently there is no standardized extract available for marijuana skin tests or allergy shots. People who cannot avoid marijuana due to their occupation – cannabis growers and narcotics officers, for example – should talk with their allergist about other treatment options.