Anxiety, paranoia, delusions and hallucinations - the perils of taking cannabis are well known.

But as marijuana use is becoming increasingly common - both for medicinal and recreational use - doctors are warning of a lesser known health risk.

The drug, like other pollen-bearing plants, is an allergen, and can cause allergic reactions similar to those suffered by people with hayfever.

Scientists found in some cases exposure to marijuana pollen or cannabis smoke provoked symptoms of allergic rhinitis, caused by inflammation of the nasal passages, causing sneezing, congestion, itching and a runny nose.

They also found symptoms of conjunctivitis and asthma.

Marijuana, like other pollen-bearing plants, is an allergen, and can cause allergic reactions similar to those suffered by people with hayfever

A new study has reviewed the medical evidence, examining cases of allergic reactions to the marijuana plant, also known by its Latin name Cannabis sativa.

The researchers wrote: 'Although still relatively uncommon allergic disease associated with cannabis sativa exposure and use has been reported with increased frequency.'

Cannabis pollen normally sheds in late summer and early autumn.

The researchers wrote it is 'very buoyant, allowing for distribution across many mile'.

Scientists and authors Dr Thad Ocampo and Dr Tonya Rans said for those people with cannabis allergies an act as simple as touching the plant can trigger hives, itching and puffiness or swelling around the eyes.

They also revealed eating cannabis products, such as cannabis seed-encrusted seafood, could trigger an allergic reaction.

After emergency treatment tests revealed the patient was not allergic to seafood but the cannabis seeds were the culprit.

And the study noted some people who injected marijuana developed reactions including facial swelling and wheezing within minutes of exposure.

Allergic asthma triggered by seasonal and occupational exposure to cannabis was also reported.

Scientists found in some cases exposure to marijuana pollen or cannabis smoke provoked symptoms of allergic rhinitis, caused by inflammation of the nasal passages, causing sneezing, congestion, itching and a runny nose, as well as conjunctivitis and asthma

The authors of the article point out that cannabis' legal status may create barriers for accurate and clear patient reporting, and that legal limitations may pose diagnostic challenges.

As with other allergens, the researchers advised that people avoid cannabis to reduce the risk of a reaction.

For those who have a history of anaphylaxis, which causes breathing difficulties, the scientists advise carrying an EpiPen.

Marijuana's legal status in the US is changing, making information about cannabis allergy timely and noteworthy.

Twenty-three states and the District of Columbia currently have laws legalising marijuana in some form, and four states have legalised marijuana for recreational use.