As the federal government inches closer to legalizing recreational marijuana, doctors are warning of an emerging health hazard: cannabis allergies.

鈥淭he more people that are exposed to marijuana, the more likely we are to see allergies,鈥 Toronto-based told 麻豆影视. 鈥淢arijuana allergy can potentially be very severe -- potentially, it can cause life-threatening reactions just like a peanut allergy.鈥

One of Dr. Sussman鈥檚 patients is Doneil Oliphant, who learned the hard way that he had a marijuana allergy when he touched his face after handling cannabis oil.

鈥淢y eyes were swollen (almost) completely shut,鈥 Oliphant recalled. 鈥淵ou could barely recognize me -- my face got a very round look to it.鈥

The symptoms lasted several hours, Oliphant said. Soon after, he found himself taking a skin allergy test at Dr. Sussman鈥檚 office and was shocked to learn that he was allergic to weed.

鈥淚 didn鈥檛 even know it was possible,鈥 Oliphant said. 鈥淢arijuana allergies (are) not something you hear about very often and so I was actually pretty surprised that I had one.鈥

With marijuana use becoming more and more prevalent, Dr. Sussman says he鈥檚 seen an increasing number of patients test positive for cannabis allergies over the past 10 years. Symptoms, he says, can range from skin irritation to respiratory issues to -- in the most severe cases -- full-on anaphylactic shock.

鈥淪kin symptoms are generally from touching it,鈥 Dr. Sussman explained.  鈥淵ou can sometimes see itchy skin and hives and you can sometimes see swelling of the eye if you touch your eye after touching the marijuana plant. Respiratory symptoms can be nasal running and sneezing with associated itchy, watery eyes. Occasionally you鈥檒l see wheezing, shortness of breath and asthmatic reactions. Anaphylactic symptoms generally occur with hempseed (or eating marijuana products)鈥 Potentially, any anaphylactic event can be serious and life-threatening.鈥

One former undercover officer with the Ontario Provincial Police told 麻豆影视 that she didn鈥檛 know she had a potentially deadly cannabis allergy until she first touched the plants while on the job.

鈥淲e were doing drug eradication, so we were pulling marijuana plants from a field,鈥 the woman, who asked not to be identified, said. 鈥淚 had a reaction to the plants which I鈥檇 never had before and my hands and forearms swelled and I got a really bad rash on them and really bad swelling鈥 I wound up having to go to (an emergency room) because the swelling and the rash was so bad that I actually couldn鈥檛 use my hands.鈥

Even inhaling second-hand marijuana smoke has sent her to hospital.

鈥淲hat happens is I get this really sharp pain behind my left eye, it鈥檚 excruciatingly painful and it鈥檚 just like a hot poker in my eye, and then my chest starts to tighten and my face gets all tingly and my arms and hands and extremities tingle and it feels like there鈥檚 just a vice in my chest where I can鈥檛 breathe,鈥 she said. 鈥淚t鈥檚 quite scary.鈥

Now, carrying an EpiPen wherever she goes, the woman worries about being increasingly exposed to marijuana smoke once pot becomes legal.

鈥淚鈥檓 not able to go to concerts,鈥 she lamented. 鈥淎nd once it鈥檚 legalized, I鈥檓 afraid (of) even just walking down the street.鈥

Like most allergies, the only truly effective way to deal with a marijuana allergy is avoidance, Dr. Sussman says.

With legalization on the horizon, Dr. Sussman has also launched the first Canadian study to see how many people have undiagnosed marijuana sensitivities. His goal is to better prepare patients and doctors -- and even potentially save lives.

鈥淚f you look at a study done out of Colorado, about 10 per cent of people just with passive exposure (to marijuana) did have sensitization or allergy symptoms,鈥 he said. 鈥淎t this point, it鈥檚 under-recognized and under-diagnosed.鈥

With files from 麻豆影视鈥 medical affairs specialist Avis Favaro and producer Elizabeth St. Philip