Although uncommon, cannabis can trigger an allergic reaction just as any other plant or pollen can. 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 by: 

• Inhaling pollen in the air
• Smoking marijuana
• Touching marijuana
• Eating marijuana

The symptoms of a marijuana allergy are usually benign and similar to seasonal allergy symptoms (dry cough, congestion, itchy eyes, nausea, red, itchy, or watery eyes, a runny nose, sneezing, sore or itchy throat) or contact dermatitis symptoms (blisters, dry skin, hives, itchiness, red, inflamed skin). These allergy symptoms occur within the first few hours after ingestions. Even less common, marijuana can cause anaphylaxis which can be life-threatening and occurs within seconds or minutes of exposure to an allergen.

To stop symptoms from getting worse, a person should immediately stop touching or ingesting their cannabis.