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People can have allergic reactions triggered by marijuana, just as they can with many other plants and pollens. Symptoms can vary from mild to severe.

In recent years, there seems to have been an increase in the number of reports of marijuana allergies. This may be because marijuana, or cannabis, is becoming more popular as a medicinal treatment for a range of conditions. Some states have also legalized the drug for recreational use.

Cannabidiol, or CBD oil, can also cause negative reactions in some people.

Read on to learn more about the causes and symptoms of marijuana allergies, and the possible effects of CBD oil.

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A marijuana allergy may be triggered by eating, smoking, or touching the plant or its products.

More than 50 million Americans have allergies. While marijuana may have some medical benefits, marijuana pollen can trigger allergy symptoms in some people.

According to the American Academy of Allergy, Asthma, and Immunology (AAAAI), a person can develop an allergy or allergic sensitization to marijuana after exposure to the plant. People can be exposed to cannabis allergens in the following ways:

  • inhaling pollen in the air
  • smoking marijuana
  • touching marijuana
  • eating marijuana

Research published in 2013 suggests a particular strain of cannabis called Cannabis sativa may be especially irritating.

A recent small-scale study from 2018 reports that people are more likely to have a cannabis allergy if they have allergies to cat dander, molds, dust mites, or plants.

More research is needed, however, to establish this possible link.

Common symptoms of a marijuana allergy, many of which are similar to seasonal allergy symptoms, include:

  • a dry cough
  • congestion
  • itchy eyes
  • nausea
  • red, itchy, or watery eyes
  • a runny nose
  • sneezing
  • sore or itchy throat

Handling the drug may also cause contact dermatitis, a skin reaction that can have the following symptoms:

  • blisters
  • dry skin
  • hives
  • itchiness
  • red, inflamed skin

Symptoms of marijuana allergies can come on immediately after exposure to the plant, although, in other cases, they may not begin for an hour or more.

To stop symptoms from getting worse, a person who notices these effects should immediately stop touching or smoking the drug.

Less commonly, marijuana can cause a severe allergic reaction called anaphylaxis. This condition can be life-threatening and occurs within seconds or minutes of exposure to an allergen.

Signs and symptoms of anaphylaxis include:

  • difficulty breathing
  • dizziness
  • fainting
  • itchy and flushed or pale skin
  • low blood pressure
  • swollen tongue or throat
  • weak and rapid pulse
  • vomiting

Anaphylaxis can result in a coma or death, so it is essential to get emergency medical attention if this reaction is suspected.

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A marijuana allergy can be linked to cross-reactivity with other allergens, including certain foods.

Along with anaphylaxis, the main risks linked to a marijuana allergy are that it may be linked to cross-reactivity with other allergens.

Cross-reactivity happens when the proteins, such as pollen, in the marijuana plant resemble the proteins in another plant. An allergic reaction may then occur when a person comes into contact with similar proteins elsewhere.

Foods with proteins that resemble marijuana proteins, and which may, therefore, cause an allergic reaction in people with marijuana allergies, include:

  • almonds
  • apples
  • bananas
  • chestnuts
  • eggplant
  • grapefruit
  • peaches
  • tomatoes

Doctors diagnose marijuana allergies in the same way as other types of allergies, by using skin tests or blood tests.

Skin tests

A doctor will first take a person's medical history and perform a physical examination. They may then use a skin prick test. This test is not very invasive, and the results come back quickly.

In a skin prick test, the doctor will apply a diluted allergen, such as marijuana, to the skin's surface with a needle. If a red bump or wheal, itching, and redness develop in that area within 15 minutes, a person may be allergic to that substance.

A doctor may also use an intradermal test. This test involves using a thin needle to inject a diluted allergen just below the skin's surface.

Blood tests

Blood tests are another way of checking for marijuana allergies. A sample of blood is drawn and tested for the presence of antibodies to marijuana. If a person has more antibodies in the blood than expected, they are more likely to be allergic to marijuana.

Blood tests may be better than skin prick tests in some cases because they involve a single needle prick. They are also less likely to be affected by any other medications. However, the results take longer to come back, and the tests are more expensive than skin tests.

At present, no treatment is available for a marijuana allergy. A person can take antihistamines to manage symptoms and reduce discomfort. Antihistamines are available for purchase online.

For some types of pollen allergy, a course of allergy shots is prescribed to reduce a person's sensitization to the substance. But these are not currently available for marijuana pollen.

Because of the lack of treatment options, those who are allergic to marijuana should avoid smoking, eating, or touching the plant or the drug to prevent allergy symptoms.

If a person has a severe allergy to marijuana, they should carry an epinephrine injection (Adrenaclick, Epipen, or others) in case of accidental exposure and subsequent anaphylaxis.

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Wearing protective layers may help to prevent an allergic reaction when handling marijuana.

Avoiding exposure to marijuana is the only way to prevent an allergic reaction to the plant or drug.

A person who is using medical marijuana and suspects that they may be allergic to it should speak with their doctor to find an alternative treatment.

People who work in a marijuana processing plant should limit exposure by using:

  • allergy medications
  • face masks
  • gloves
  • inhalers

Cannabidiol (CBD) is a substance that comes from the marijuana plant. Medicinal uses include treating some seizure disorders.

CBD is different from tetrahydrocannabinol (THC), the psychoactive substance in marijuana. Pure CBD does not have mind-altering effects. Only THC produces these "highs."

In contrast, CBD may have antipsychotic and anti-inflammatory properties.

The United States Food and Drug Administration (FDA) has only approved one CBD-based drug, Epidiolex. This prescription-only treatment can help people who have two types of rare and severe epilepsy. The drug received approval in June 2018.

For most uses, research has not yet confirmed how safe and effective CBD- or marijuana-based products are, and there are no regulations controlling the production or sale of CBD oil and other marijuana products.

Some CBD products contain THC, but it is not always clear how much, even when there is a label.

For this reason, most consumers do not know how safe their CBD oil is, especially when used in high quantities.

A 2011 review of previous studies on CBD oil reports conflicting findings. The researchers suggest that, while long-term use and high doses up to 1,500 milligrams a day may be well tolerated by people, some adverse reactions have been observed.

At high intakes, CBD oil may cause:

  • drowsiness
  • dry mouth
  • interactions with other medications
  • lightheadedness
  • low blood pressure

A 2017 study recommends more research be carried out on the effect of CBD on certain enzymes, drug transporters, and the effects of other drugs.

Some people use CBD oil as a topical treatment for skin disorders or neurological pain. A person should try applying a small amount of the oil first, to ensure they will not experience an unwanted reaction.

In addition to Epidiolex, the FDA have also approved three drugs that contain a synthetic form of THC. Marinol and Syndros treat the severe weight loss that can occur with AIDS. Cesamet can help prevent nausea and vomiting in people who are undergoing chemotherapy for cancer.

As with other medications, it is possible to experience an allergic reaction to Epidiolex, Marinol, Syndros, and Cesamet.

Most people with marijuana allergy symptoms have a mild to a moderate reaction that is similar to seasonal allergy conditions. Skin reactions may also be experienced.

When a person avoids the drug and its pollen, their symptoms will resolve quickly.

Those who are severely allergic to marijuana should seek medical treatment. Also, they should carry medications to react quickly to accidental exposure to the drug.