Mast cells are part of the innate immune system and responsible for the release of hundreds of pro-inflammatory chemicals, the most well-known being histamine. Mast cells are famous for their involvement in allergic disorders, and the release of their contents on contact with certain allergen "triggers."

Symptoms associated with a "mast cell disease" from wikipedia:

Fatigue
Skin lesions (urticaria pigmentosa) and itching
Abdominal discomfort
Nausea and vomiting
Diarrhea
Food and drug intolerance
Olfactive intolerance
Infections (bronchitis, rhinitis, and conjunctivitis)
Ear/nose/throat inflammation
Anaphylaxis (shock from allergic or immune causes)
Episodes of very low blood pressure (including shock) and faintness
Bone or muscle pain
Decreased bone density or increased bone density (osteoporosis or osteosclerosis)
Headache
Ocular discomfort
Malabsorption

I wanted to start a thread on this topic to see if anyone has researched mast cells, and ways to stabilize (mast cells) and mitigate reactions.

I've had some decent success with green tea extract, after finding good evidence that it is mast cell stabilizer.